Evaluation of the impact on women's lives of the introduction of low cost polyethylene biodigesters on farms in villages around Ho Chi Minh City, Vietnam

Mette Ide Lauridsen

Department of Political Science, University of Aahus, Aahus, Denmark
Mette.Ide.Lauridsen@get2net.dk

Abstract

The introduction of polyethylene biodigesters in villages around Ho Chi Minh City has had a very positive impact on the lives of women. It has reduced their workload because they save time on collecting and buying firewood and on cooking. It has also other advantages such as a better and cleaner environment on the farms and in the kitchen, cleaner pots and pans, and saving of money. The improvement of women's lives is one of the main reasons why it is important to spread out the technology of polyethylene biodigesters to other parts of Vietnam and to other countries. When planning further extension of the methodology more attention should be paid on involving the women in the process by holding information meetings, training courses and by contacting them directly on the farms. If that is done the introduction of biodigesters could also have a positive impact on the social life of women.

Key words: Women, biodigesters, extension, quality of life

Introduction

Even though the past century has been a period of change and progress in the developing world there is still a lot to be gained in many areas, especially with regard to the environment.  Many developing countries are facing serious environmental problems because of increasing population and because of development activities which lead to increased demand for fuel and more pollution (Marchaim 1995; Bui Xuan An 1996;  Bui Xuan An et al 1997). These environmental problems have led to a focus on the need for sustainable agricultural development and for renewable energy sources in the developing world (Preston1995; Luu Trong Hieu et al [editors]1994). As a consequence, biodigesters have been installed in many countries as an alternative to traditional energy sources ( Marchaim 1995; Preston 1995; Bui Xuan An et al 1997; Moog et al 1997).

The introduction of biodigesters has many economical, environmental and social benefits. Biogas is one of the cheapest renewable energies in rural areas in developing countries. The use of biodigesters is good for the environment because biogas replaces firewood, and the process of anaerobic digestion reduces pollution otherwise caused by untreated excreta from livestock and people. Biodigesters are beneficial for integrated farming systems because they convert manure to an improved fertiliser for crops or ponds for fish and water plants (Bui Xuan An 1996). Furthermore, it is claimed that biodigesters have a positive impact on women's lives (Bui Xuan An 1996; Vliet et al 1996). However, no scientific research on this aspect has been done until now. This study focuses on the impact on women's practical and social lives of the introduction of polyethylene biodigesters in villages around Ho Chi Minh City.

Women's practical and social life - a theoretical introduction

Theories have been developed and research has been done in the area of women and gender in development since the 1950s (Mikkelsen 1995). Within the last 15 years theories and tools for gender analysis have also been developed and found very useful in the field of agricultural research. Today it is widely accepted that women's as well as men's views, and the understanding of gender differences, are important in helping science shape improved technologies for agricultural development and to meet the needs and fit the circumstances of small farm households (Feldstein and Jiggins [editors] 1994).

When making an analysis on women it is important to recognise their triple role; that is their role as reproducers (child rearing, child bearing), producers (work done for payment, home production) and their community management role (activities undertaken by women at the community level) (Mikkelsen 1995;  Brzeski 1996). It is also important to focus on their practical - as well as their strategic gender needs. Practical gender needs are those identified by women and men which arise out of the customary gender division of labour. Strategic gender needs reflect a challenge to the customary gender relations and imply changes in relations of power and control between men and women (Mikkelsen 1995; Brzeski 1996; Feldstein and Jiggins 1994).

These roles and needs are included in this analysis by focusing the evaluation of the impact of biodigesters on women's lives on two dimensions:

• The practical life: that is the role as reproducer and producer and the meeting of practical gender needs, e.g. the kind of farm production activities done by the woman, how much time does the woman spend on the different activities, how has the introduction of biodigesters changed these activities.
• The social life: That is the community management role and the meeting of social gender needs, e.g. what is the social status of the woman, what kind of resources are in the control of woman, what decision-making authority does the woman have, how much does the woman participate in the life of the community and what is the relationship between men and women and is it changing?

Research Design

The research design is inspired by Qualitative Research Methods, Participatory Rural Appraisal (PRA) and Rapid Rural Appraisal (RRA) and use of the research tools recommended by these methods. Researchers using qualitative methods strive to understand situations as a whole. They try to understand the totality and the unifying nature of particular settings and assumes that the whole is greater than the sum of its parts. Therefore the description and understanding of a situation context is essential for understanding the situation. The methods are inductive which means that the researcher tries to make sense of the situation without imposing pre-existing expectations on the setting, e.g. not presupposing what the important dimensions of the evaluation will be. The methodological tools used by evaluators using qualitative methods can be observations of participants, unstructured or semi-structured interviews with key-informants or ordinary members of the target population (Casley and Lury 1988).

PRA and RRA were developed in the 70´s and 80´s as a critical reaction to the traditionally used quantitative and qualitative research methods. Some of the elements they have criticised are the separation between theorists and practitioners, the separation between the people from the villages and the researchers and the slowness of many of the research methods used in development research (Chambers 1983; Mikkelsen 1995). These new methods stress multidisciplinarity, participation and rapidity. The tools used are many (e.g. the use of secondary information, key-informant interviews) and the use of different tools at the same time is regarded as important (RRA 1994).

The information for this evaluation has been obtained in different ways.

• Living in Vietnam for two months. While living in the country the author has learned a lot about the Vietnamese country, its people, culture, agriculture and the role played by women in the Vietnamese society
• Use of secondary information: literature about gender and development, gender and agriculture and sustainable agriculture. Evaluations on women and livestock production and women and biodigesters in other countries. Scientific reports from Vietnam about the everyday life of women and the introduction of biodigesters.
• Six  informal, conversational and topic-focused interviews with key-informants (researchers, extensionists, representatives from the Women's Union, demonstration farmers)
• Thirty three informal, conversational interviews with men and women from farms with and without biodigesters
• Eleven open-ended interviews with women living on farms with biodigesters. For these interviews a questionnaire was used.

When obtaining information on gender it is important to notice that a general rule is that information on gender-sensitive issues should be obtained from women and men separately (Mikkelsen 1995). Some information about the social life, e.g. roles in decision making in the family of the women, can be very difficult to get because it is hard to operationalize and ask directly about it (Rangnekar 1994 ).

Women's situation in villages around Ho Chi Minh City

On the basis of  visits to farms, and informal and open-ended interviews with key-informants and women farmers, an impression was obtained of the everyday lives - practically as well as socially - of women in villages around Ho Chi Minh City.

The practical life of the woman

It is  the women, according to key-informants and secondary literature (Bui Xuan An et al 1994), who are responsible for a lot of working activities concerning the household, livestock production and other agricultural production activities on the farms. It is the women who take care of the children, cook the food, go to the market, collect the firewood, take care of the animals and they also help with the field work and other related activities. Vietnamese men work less on the farm than women and they mainly take care of activities which result in their absence from the household environment, such as work in distant field plots and attendance at meetings.

In the open-ended interviews, questions were asked about which activities the families had on the farm and which persons did that work. Table1 shows how the workload is shared between different members in the family.

Table 1: Workload between different members in the family.
Number of farms where the activity is done by: / Activity	Only the Woman	Only the Man	Woman and Man	Woman and Children, Grandparents or other	None	Total
Cooking	9	0	0	2	0	11
Taking care of animals (pigs)	5	1	2	3	0	11
Collecting or buying firewood	5	0	1	4	1	11
Working in field, fish pond or fruit garden	2	0	3	3	3	11
Other activities	0	3	1	2	5	11
Total	21	4	7	14	9	55

It is always the woman who cooks the food for the whole family, sometimes other women in the family help, e.g. the daughters of the family or the grandmother or mother-in-law. Women are also in charge of taking care of the animals. They are the ones who feed the animals, clean the pig pens etc. Women also collect the firewood. In families where the firewood is bought, this may be done by other members of the family.

Women also help with all the other activities on the farm like taking care of the fruit gardens and working in the rice fields, but they are not the persons in charge of this work. Only one of the women had other work than on the farm. She was a teacher. But three of the men had jobs outside the farm.

The social life of the woman

From key-informants and through farm visits a lot was learned about the social life of women. Even though women work a lot on the farms they also have the time for a social life. When visiting the farms it often happened that the woman was not present. Sometimes the women were having a party with other women from the village or family members, and sometimes they were at the market to buy or sell goods needed or produced by the family. In every village in Vietnam, there is a Women's Union where many women take active part in arranged meetings and activities. They have different activities in different villages. The branches of the Women's Unions around Ho Chi Minh City focus their activities on family planning and credit systems and not have activities on agricultural development. The latter is only done by farmers' unions and extension centres.

Traditionally the man is the head of the family in Vietnam. He is the one who can take the decisions concerning the family and the farm. He is also the one who represents the family in the community: he participates in meetings at the community level and he is the one who welcomes and talks to visitors when they come to the farm. When the extension centre invites one representative from the farm to information meetings about new agricultural techniques it will almost always be the man who shows up. And when extensionists and university staff go to the farms it is always the man who welcomes and talk to them. However there is no problem to talk to the woman if the man is not at home or if you explicitly ask to talk to his wife. Asking to make an interview with the women in the family was always welcome, but if the man was on the farm he would stay during the interview and give comments on the questions and the answers given by the woman.

The introduction of polyethylene biodigesters around Ho Chi Minh City

More than 1000 biodigesters have been installed in Vietnam and about 400 of these have been installed in villages around Ho Chi Minh City (Nguyen Duong Khang 1996). At present, material for one new biodigester is sold every day from the distribution centre at the College of Agriculture and Forestry, Ho Chi Minh City. Compared to other countries the introduction of polyethylene biodigesters in Vietnam and especially in villages around Ho Chi Minh City has been a success. This is evident from the numbers of biodigesters that have been sold and because they are working well (Bui Xuan An 1996). Part of the success is due to the extension methodology.

The promotion of biodigesters in villages around Ho Chi Minh City has been done through a close relationship between researchers, exensionists and farmers.  The participation of the farmers, and farmer to farmer contacts, have been given a high priority. According to Dolberg (1994) and  Bui Xuan An (1996) this is a very important factor for the successful extension of technologies. Figure 1 illustrates this approach.

Figure 1: Illustration of the extension methodology used to spread the biodigester technology

At the University of Agriculture and Forestry, researchers have been doing research on the technology of biodigesters (Bui Xuan An et al 1994, 1997). The researchers have disseminated their knowledge of the technology by holding training courses for extensionists at the University and directly at the extension centres in the region. The researchers are also in direct contact with the farmers. They go to the farms to install the biodigesters, discuss the technology with the farmers, discuss problems with them and answer questions about the biodigesters. But they also get feedback from the farmers because it is important for the researchers to know how the technology works in practice, so the researcher can accumulate knowledge about the technology and improve it. All the farms that were visited had been in contact with researchers from the University. Either because the researchers had installed the biodigesters or because they had visited the farm. The researchers have also participated in training courses and information meetings for farmers and they have produced an information pamphlet for the farmers about the technology.

In 1993 the Ministry of Agriculture and Food Industry established an Extension Department to carry out activities such as: extension of knowledge of economy and technology to farmers, training and enhancing the living standard of farmers and developing rural socio-economy. At present, there is an extension centre in each province and a station in each district. The extension centres have played an important role in the dissemination of the polyethylene biodigester technology. Around Ho Chi Minh City they have helped to choose the demonstration farms and arrange information meetings for other farmers on the demonstration farms.

However, most important for the extension of the technology, is that there has been a positive dialogue between farmers. Farmers have to be convinced that this new technology works to invest in a polyethylene biodigester. The experience is that they only are convinced if they see the system working on another farm. That the farmer-farmer relationship plays an essential role in the extension is the impression got through key-informants and during farm visits.  The results from the questionnaire confirmed these impressions.

In the questionnaire the families were asked from where they had got the information about the biodigester. Table 2 shows the source of this information.

Table 2: Source of information about the biodigester
	University	Other farmers	Mass media TV or newspaper
Number of farmers	2	8	2
Note: One farmer received the information from two sources: other farmers and  the Mass media

Eight out of eleven farm families got the information from other farmers who in turn told other family members or neighbours.. The two farms which got the information from the University were demonstration farms. The demonstration farms are very important to create a link between researchers and extensionists on one side and farmers on the other side. If a farmer agrees that his farm can be a demonstration site for the biodigester technology he only pays 50% of the price of the biodigester, the rest is paid by a technical assistance project (FAO/SAREC). The demonstration farmer then has to help the researchers collecting data about how the biodigester works and he / she has a very important role to play in order to create a dialogue among farmers. Furthermore, information meetings for other farmers will be held on the demonstration farm.

The extension methodology has had a focus on men. Researchers and extensionists told that they mainly communicated with the men and the Women's Union had not been involved in the extension. In the questionnaire, some questions were asked in order to to find out how much the women had been involved in the project.  The results show that the man mainly has been involved (Table 3).

Table 3: Persons in the family involved in the project.
Person involved	Woman	Man	No answer	Total
First contact	2	6	3	11
Helped by installing	0	5	6	11
Fixed technical problems*	0	3	2	5
* Only five of the families have had technical problems with the biodigester

The impact on women's lives

In the literature about biodigesters it is often mentioned that it improves the lives of the women (Bui Xuan An 1996; Rodriguez et al 1996). This fact has been confirmed by many of the key informants, met when visiting the farms and by asking questions. When interviewing the women, it was found that the introduction of biodigesters gave rise to several advantages and only a few or no disadvantages concerning the practical lives of the women (Table 4).  However, it seemed there had been no direct effects on the social life of the women.

Table 4: Advantages and disadvantages mentioned by the women in villages
	Number of women mentioning it
Advantages mentioned Saves time Cleaner environment Cleaner pots and pans Saves money Easier and more comfortable than firewood You can do other things while you are cooking Avoid problems with firewood in the rainy season Kitchen is cleaner Slurry is good for fertilising	8 8 8 6 4 3 2 2 1
Disadvantages mentioned Disagreeable smell Have to move the manure Stove is not good Low pressure of gas in the rainy season Quantity of manure varies	2 1 1 1 1

The advantages

Saves time:

One advantage mentioned by all the women is that the introduction of biodigesters saves time. The time is saved in many ways and on different activities done by the woman. First of all, the woman saves the time used to get a source of fuel for cooking. Table 5 shows the previous sources of fuel for cooking and the time spent on getting the fuel before and after getting a biodigester.

Table 5: Previous sources of fuel for cooking and time spent on getting the fuel before and after getting a biodigester
Name of woman	Previous source of fuel	How to get it	Time spent before	Time spent now
1. Mrs. Ming	firewood	bought at market collected	2˝ days / month	Collect firewood when having parties
2. Mrs. Big	firewood	bought at market collected	1˝ hours every second day	Collect firewood when having parties
3. Mrs. Hoang	firewood gasoline	bought	did not know	did not know
4. Mrs. Dung	firewood	collected	˝ hour every day
5. Fam. Huong	firewood	bought through middleman	very little	very little
6. Fam. Tam	firewood	collected	did not know	did not know
7. Mrs. Chung	firewood	bought through middleman	very little	very little
8. Fam.Thanh	firewood	bought through middleman	very little	very little
9. Mrs. Dung	electric cooker
10. Mrs. Anh	firewood	collected	1 hour per day	no time
11. Miss. Huong	firewood	bought through middleman	very little	very little

The main source of fuel before the introduction of biodigesters was firewood in almost all the families. Some families had been supplementing with other sources of energy such as electric rice-cookers, industrial gas or gasoline and in one of the families they only used gasoline and an electric cooker before they got the biodigester. The time saved on getting fuel for cooking varied a lot and sometimes it was hard for the women to tell exactly how much time they spent on this activity. The women who used an electric cooker before saved no time, because these sources of energy are just as quick to use as biogas. The woman who bought the firewood through a middleman only saved a little time. The group of women who saved most time are the five women who had to go to the market themselves to buy the firewood or who had to collect the firewood on their land or in their fruit garden before they got the biodigester.

Some women mentioned that they spend more time to get firewood in the wet season (from May to October) because they had to dry the firewood in the sun. It is a very time-consuming process, because every time it starts raining the women have to collect all the firewood and put it under shelter and when the rain stops it takes time to spread the firewood out to dry again. The women told that they also saved time when cooking food for the family. By asking question on how much time the women used on cooking before and after they got the biodigester it was found out that eight out of the eleven women saved time on cooking (Table 6).

Table 6: Time spent on cooking before and after getting a biodigester.
	Time used in hours
Name of woman	Before	After	Difference
1.   Mrs. Minh	5	3	- 2
2.   Mrs. Bich	1˝	1	- ˝
3.   Mrs. Hoang	3	1˝	- 1˝
4.   Mrs. Dung	4	3	- 1
5.   Fam. Huong	3	2	- 1
6.   Fam. Tam *)	-	-	-
7.   Mrs. Chung	3˝	2	- 1˝
8.   Fam.Thanh	6	6	0
9.   Mrs. Dung	7	7	0
10. Mrs. Anh	7˝	5˝	- 2
11. Miss. Huong	8	8	0
Median value	4 h 30 min	2 h 30min	-2
* The husband was interviewed but did not know how much time his wife spent on cooking

The women who did not directly save time on cooking, mentioned that biogas was quicker, therefore they could do other things while cooking. To find out if the time saved on cooking and buying and collecting firewood was real, the women were asked how much time was needed to manage the biodigester.  The answer was that it took some time to install and repair the biodigester, but that this work was always done by the men in the family or by University staff. After the biodigester has been installed most of the women did not have to spend extra time to manage the biodigester. They just cleaned the pig pen every day as they did before. In two of the farms it was necessary to move the manure or some of the manure from the pig pens to the biodigester. This work was usually done by the women in the family, but they could not tell exactly how much time was used.  One women answered that the work was very little; another said it took 15 minutes. The overall picture is that the women saved some time every day after getting a biodigester.

The women were asked how they used this extra time. Four women spent the time doing all the other activities on the farm. Three had more time to rest and relax and one mentioned that she now had more time to take care of her husband and children. Four of the women couldn't answer the question.

Cleaner environment:

Eight of the women who were interviewed, and many other women and men from farms that were visited, mentioned that an important and very positive impact of the introduction of biodigesters had been a cleaner environment. The immediate environment (the space arounnd the house and the pig pens) was better and cleaner after the introduction of biodigesters for many reasons.

First of all the treatment of the pig manure reduces its smell. The women found this fact very nice for themselves and their families. The pig pens are always placed very close to the house or connected to the house. But two women also mentioned that it was a very important advantage because it had led to a better relationship with the neighbours. Around Ho Chi Minh City the farms are very close to each other and if one farm keeps pigs the smell will go to many other farms. Some of the farms that  were visited had had complaints from their neighbours before they got the biodigester, but subsequently these problems had been  solved.

The environment in the kitchen where the women spend a lot of their time every day was also better after getting a biodigester, because firewood leads to a lot of smoke and biodigesters do not. The women answered that they found it very nice that there was no smoke in the kitchen and in the rest of the house. The smoke can especially be a problem during the rainy season when the firewood is damp. The treatment of the manure also reduced the amount of flies on the farm.

Cleaner pots and pans:

Eight women mentioned that their pots and pans were cleaner after they started cooking by biogas and they found that very saatisfactory.

Saves money:

As a fourth advantage of the biodigester, six women mentioned that it saved money. The amount of money saved varied a lot. Only four women could give an exact answer. These women saved 24, 15, 10 and 3 dollars per month. The average price of a biodigester in villages around Ho Chi Minh City was around 35 dollars initially, but has now risen to 45-50 dollars. The payback time is on average 5.4 months (Bui Xuan An 1996). That is, in about 5 to 6 months the money saved on buying firewood or gasoline, has paid for the biodigester.

Disadvantages

Two women mentioned the disagreeable smell. When the women were used to the smell of firewood they often found the smell of biogas strange and some of them thought, or were told, that the smell was bad for their health. This problem can be solved by informing them that the smell is different, but that it is not dangerous. Some of the women had to move the manure. One of them mentioned this as a disadvantage. The problem can only be solved by moving the biodigester.

Other women mentioned that the amount of biogas and the gas pressure varied because the amount of manure varies or because less gas is produced by the biodigester in the rainy season. A solution to this problem is to store the manure when they have too much or get manure from other farms when they have too little. If there are problems with low pressure of the gas they have to learn how to increase the pressure by pressing on the reservoir, putting something heavy on top of the reservoir or put a rope around the reservoir and increase the pressure by pulling on the rope.

One woman mentioned that her stove was not very suitable. It is important that the flame gets spread, otherwise it is slow to cook with biogas. It is possible to buy suitable stoves costing about USD5.00.  They can also be made from local materials. On one farm a shower head was used to spread the flame.

Impact on practical and social life

This investigation has shown that the introduction of biodigesters has had a very positive impact on the practical life of women, mainly because it has reduced their workload because they save time getting firewood and in cooking. With a biodigester it is easier and cleaner to work in the kitchen and on the farm. There appeared to be no direct effect on the social life of the women. They never mentioned that the introduction of biodigesters had changed their role in the community, their level of participation or their relationship to their husbands. It is also worth noting that none of the participants answered that they used the time saved on social activities outside the family.

Discussion

The extension methodology used in villages around Ho Chi Minh City has been very efficient. Many biodigesters have been installed in a short time and most of them are still working. But the focus of the researchers and extensionists has primarily been on men. The reason for this is that it is the man who is the head of the family and who can take decisions about whether the family invest in a biodigester or not. Another reason is that researchers and extensionists traditionally have been working with men in agricultural development.

It is suggested that it is important to pay more attention to women when planning further extension of the polyethylene biodigesters. To speed up dissemination of the biodigester technology it is important to inform women as well as the men about the advantages of the biodigesters, to teach them about the technology and involve both women and men in the decision about getting a biodigester. This is important for many reasons:

It is important that women know about the biodigester technology, because it is the women in the family who can benefit the most from getting a biodigester. If they come to know about the technology and the advantages that is has for them, many women would like to get a biodigester and if they have the power to take a decision of getting it, the dissemination of the technology could speed up.

It is important that the woman who know how to monitor and adjust the biodigester, because it is the women who spend most time in the vicinity of  the biodigester.   It is important that she is motivated, interested and takes care of it. Many problems with biodigesters are caused by lack of attention: e.g. animals or children destroy the biodigester because it has no fence around it. Falling objects, such as branches, make holes in the plastic because the biodigester is not covered well.

Because it is the woman who feeds the animals and cleans the pens it is important that she is informed about the latest findings on the technology (eg:  investigations on the best loading rates and what kind of manure is best to produce gas) (Preston 1995; Bui Xuan An 1996), so that these findings can be useful in practice. Contact between women and researchers and extensionists is also very important to improve the technology. Because women work with the biodigester and cook with the gas,  they find a way to solve problems of low gas pressure, holes in the plastic and similar difficulties.  It is important to continually collect this information and disseminate it to other farmers. Researchers and extensionists can learn a lot from the experiences of the women. Involving women in the extension of biodigesters could lead to a better social position for them, because it would give them knowledge, decision power, responsibility and an opportunity to participate in meetings and meet other women.

Conclusion

The introduction of biodigesters on small farms in villages around Ho Chi Minh City has had a very positive effect on women's practical lives. They save time every day on cooking and collecting firewood and they mention many other advantages such as a cleaner environment in their kitchen and on the farm, cleaner pot and pans and that they save money, because they no longer have to buy firewood or other traditional sources of fuel.

Many women in other parts of Vietnam and in other countries could also benefit from the biodigester because the life of the women in villages around Ho Chi Minh City is similar to the lives of women in countries all over the world. In many countries they are the ones who cook, take care of the animals and collect the firewood (Feldstein and Jiggins 1994; Rangnekar 1994; Vliet et al 1996).

It is important to pay more attention to women and involve them more when planning further extension of the technology. This would be beneficial to speed up the dissemination, to extend the lifetime of biodigesters, to make new useful knowledge in practice, to improve the technology and to strengthen the social role of women.

Acknowledgements

The present study was made during a stay at the University of Agriculture and Forestry, Thu Duc, Ho Chi Minh City, Vietnam in July and August 1996.  The author would like to express her sincere thanks to:

Dr. Bui Xuan An for his supervision, and for his advice, support and help while making this study. She also wants to thank him for his kindness and hospitality during her stay in Vietnam.
Dr. Luu Trong Hieu for his helpfulness and hospitality
Mr. Nguyen Duc Anh for driving the author to the farms and translating the interviews.
Mr Duong Nguyen Khang, University of Agriculture and Forestry, Ho Chi Minh City;
The Representatives from the Women's Union in An Son Village, Thuan An District, Song Be Province;
All the women who were interviewed for spending their time answering the questions and for the invitation to their houses.
The leaders of the Extension Centre in Song Be Province;
The extensionists in Long Than My Village, Thu Duc District, Ho Chi Minh City.
Lylian Rodriguez and Dr T R Preston for their friendliness and helpfulness during the stay in Vietnam and their assistance in the work related to this study.
Mr. Hai, Mrs. Loc, Mrs. Nhan and Mrs. Dong for their kindness and hospitality.
Mr Frands Dolberg for the opportunity to work in Vietnam and for his supervision, support and help before, during and after the stay in Vietnam.

References

Received 30 August 1998

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