Trees are gods: the sanctification of forests in the traditional worldview of the co tu people in Vietnam

In the living world, only human beings have beliefs and act according to their viewpoints on values. Beliefs and values form an essential part of the culture/ethnic culture. What is the composition of beliefs and the scale of values dependent on? It is a question whose answer has not come from any particular academic discipline. It is just known that the first catalyst that creates people’s beliefs and viewpoints on values is the environment that emphasizes the intimate relationship between humans and the environment. Croll and Parkin called the environment which humans inhabit and adapt to for their existence ecocosmology . “…That world is in a way that people will consider themselves to be inseparable from it” [Croll & Parkin, 1992, p. 3]. Arhem Kaj interpreted more specifically that the ecocosmolog y included two complementary worldviews: totemism and animism. “Those two worldviews create an overall ecocosmology that helps shape awareness, guide practices, and give meaning to life” [Arhem, 1996, p. 186]. It is known that in anthropology, totemism and animism are considered primitive forms of religion [Tylor, 1871]. Totemism ascribes images of nature to human society; animism uses descriptions of society to construct natural order. However, from another perspective, in the concept of ecocosmology , these two theories can be considered as types of existence that discuss the relationship between humans and nature [Descola, 2012]. According to that ecocosmology , humans are a part of the natural environment. Such living things as trees, animals, etc. are considered entities equal to humans, living in the same environment as humans. The relationship between humans and nature is a social or subject-subject relationship, also known as inter-subject, with mutual negotiation and exchange [Nurit, 1993; Descola, 1996; 2012; Ingold, 2000; Arhem and Guido, 2016]. In the connotation of that relationship, trees are a reciprocal subject that scholars pay the most attention to. In studying the symbolic meaning of trees, the image of trees in humans’ abstract worldview has become a popular research topic in world science. Frazer in Chapter IX of Golden Bough, argued that belief and “intersubjectivity” between humans and plants give rise to the worship of trees [Frazer, 1923/2007]. M. Durkheim also emphasized the symbolic value of plants as part of the landscape in his studies. Laura Rival, along with many other scholars in The Social life of trees and Anthropological perspectives on Tree symbolism, also discusses how tree symbolism reflects the human urge to express ideas through external and material signs, no matter what these signs might be [Laura Rival, 1998]. And many case studies published in academic forums discuss how the world's peoples interact with trees and the tree image in their worldview.

Trees are gods: this thought has existed for a long time and has been popular in the mindset of the Co Tu community, an ethnic minority among 54 ethnic groups in Vietnam. Trees are a product of the natural world, but for the ethnic group, trees are considered a subject in parallel with the human world, where there are levels of emotions, beliefs, and actions towards viewpoints on values. This study contributes one more voice in discussing the relationship between humans and the natural world that humans always try to impose their knowledge and will on the natural world and attach themselves to myths, values, and beliefs. People regard themselves and the natural world as associated inter-subjects. The purpose and the novelty of the article are to take a closer look at the Co Tu people’s perceptions of the plant worship cult and how they have sanctified forests through that cult. They attach essential roles and positions to the woods that are inseparable from their lives. They have created customary law to protect the sacredness of forests. In promoting relationships with nature, protecting and preserving the environment, these indigenous practices are a very positive form that should be encouraged.

2.    Field site and methodology

The Co Tu ethnic minority is one of the ethnic groups belonging to the Mon-Khmer languages, the Austroasiatic language family. They live in Vietnam and Laos, with about 74,173 people [General Statistics Office, 2019]. In Vietnam, they reside mainly in the three mountainous districts of Tay Giang, Dong Giang, and Nam Giang of Quang Nam province. They live in Phu Tuc hamlet, Hoa Phu commune and Ta Lang and Gian Bi hamlets, Hoa Bac commune, Hoa Vang district, Da Nang city. And there is a part that resides in Nam Dong mountainous district, A Luoi mountainous district and Binh Dien commune, Hong Tien commune in Huong Tra town, Thua Thien Hue province. In Laos, they reside in several regions such as Sekong, Saravane, and Champasak. Like the mountainous areas in the Annamite Range in Vietnam, these districts have rough and dangerous terrain, located among high mountain ranges, divided by many rivers and streams, with steep slopes and swift flow. Most residential areas divide into three types of terrain: high mountainous regions, low mountainous areas, and hilly valleys.

The Co Tu ethnic group has many different names and pronunciations Katu, Co Tu, Co tu, K'tu... However, the spelling and name officially recognized by the State of Vietnam and used in administrative documents since 1979 1 have been Co Tu / Co-tu. Here, we choose to use “Co Tu” because this name is confirmed in the List of Vietnamese ethnic groups (1979).

Due to their residence in mountainous areas, their main livelihood includes traditional cultivation and gathering, hunting and fishing. They have conventional crafts of knitting and weaving. The highlight of the community’s material culture, in general, is the image of the Guol house. Guol is located in the center of the village, where everyday rituals are performed. Means of transport include travel on foot, bicycle or motorbike. Their costumes can be divided into two categories: daily clothes and festival clothes. The daily meals of the people are straightforward with rudimentary processing techniques. The main spices are salt, fish sauce, monosodium glutamate. They often use the roots and leaves of forest trees to make drinking water. The spiritual life is associated with a system of festivals and rituals spanning the agricultural production cycle and the human life cycle.

This article results from our intermittent ethnographic field trips between 2009 and 2020, focusing on 2017–2019. We collected the article’s data mainly through three methods: unstructured indepth interview, semi-structured interview, and group discussions. Interviews were conducted mainly in the common language (Vietnamese) with the assistance of indigenous interpreters. The interviews lasted one to two hours per person. Since these intermittent field trips lasted many years, we built a close relationship with the people. Often, we stayed in their houses all day, joining the daily activities of the villages and families. These are valuable participatory observational experiences in the ethnographic fieldwork that we call “embodiment and trust-building.”

To learn and collect information to gain insight into the ecocosmology of the community, we determined the sampling for the interviews to be intentional (rather than random). The sampling for these interviews was intentional [Bernard, 2006, pp. 189–191] 2. The subjects were divided into four main groups: village elders / older people, females aged 30–50, males aged 30–50, and young people (both males and females) under 30. The collected interview data was analyzed manually by carefully reviewing the interviews, audio recordings, and other information to identify critical topics related to the research story.

To summarize, in the main period 2017–2019, we conducted nine semi-structured in-depth interviews with village elders / older people in the village; nine unstructured in-depth interviews with females; nine unstructured in-depth interviews with males; nine unstructured in-depth interviews with females and males under 30; nine unstructured in-depth interviews with local officials. There were also two group discussions with those aged 50–70 and those aged 30–45. The selection of interviewees and multiple age groups helped us access different perspectives on their beliefs, attitudes, and behaviors related to the research matter.

3.    Findings and Discussion3.1.    The appearance of the forest god

A tree in the Co Tu language is known as ariec . According to the ethnic group, plants are seen as a living entity with strength and feelings for the surrounding species, even understanding human aspirations. The progress and results of the group discussions and individual interviews both showed a respectful attitude of the members towards trees, especially for large-stemmed, perennial trees. The system of ethnic folk tales ³ has recorded the popularity of stories with the motif that trees have souls like humans. The stories about plants with evil souls such as Chpơơr, Achul, Azil, Dong Clui, Prong ⁴ were shared whispering by the discussion group members. They believe that if these trees are cut down, the souls will come back to harm the villagers and break the house roofs, so no one dares to approach them. The people regard trees as a living entity, thinking and acting like humans.

Looking broadly at other studies in anthropology or social sciences and humanities, we see that the belief in certain plants expressed through reverence or fear of the Co Tu people in Vietnam is not unique. According to Fraze, people’s trust in trees occurred very early [Fraze, 1923/2007, p. 189]. People believe trees have souls like themselves, so they treat them accordingly [Ibid., p. 192]. The Co Tu village elders believe that if people have three relationships in three realms of space: the subterranean realm (the world of the dead); the present time realm (the world of the living), and the ethereal realm (the world of the gods), so do trees. Trees also have communication with three spatial layers: the underground is where trees strike deep roots, hide them and take the essence of the soil to maintain the existence of the trees; the ground is where trunks with branches grow; and the overhead space of trees is the soaring sky that has created the stance of the entities above the trees, where the branches spread far away, and treetops rise to absorb the sunshine. Annually, leaves fall and then grow again, which is a symbol of rebirth. It is that existence that gives trees lasting and robust vitality. That vitality also creates a close-familiar image and belief in the ecocosmology of the ethnic group that there are souls in trees. The souls that reside deep in the tree trunks are called abhui. However, according to Nguyen abhui is not just a specific name for tree souls, but a general term for supernatural entities in the natural world, “concept that includes souls associated with all the manifestations of nature that we can see in rivers, streams, grounds, water, rocks, mountains, plants…” [Nguyen, 2004, p. 339]. Here we only discuss the meaning of the word abhui in the narrow sense, which is the soul of trees, called abhui tree.

“ Plants are just like people. From seed or a seedling, a tree will grow tall, then it will also dry up, grow old and die like us, so it also has a soul, called abhui tree ” (Interview with the man, 65 years old, in 11/2017).

“ Abhui has many types, different personalities. The abhui forest mainly inhabits in the forest. Abhui residing in any tree has the same characteristics as that tree. The large, perennial woody tree is where the great abhui dwells, possessing extraordinary powers, profoundness, and tolerance. This abhui always protects human life. Plants containing many poisons are where the evil abhui resides, so people should not approach them ” (Interview with the man, 84 years old, in 11/2017).

Tylor [1871/1958] called the phenomenon that people believe in the existence of souls’ animism ⁵ is a naturalistic view, which is a religious view that gives life to nature with types of souls. “Those souls also have living activities like humans: eating, sleeping, hunting, farming… taking place on the same living space of humans” [Ahem, 2009, p. 93]. The Co Tu peoples value trees and consider each tree to have a soul ( abhui ). Many trees come together to form forests, and a forest has been seen as a significant deity ( Yang ). Yang is the forest god who gives food and arranges the order of life to ensure peace for the community.

The Co Tu people’s leading economy is traditional agriculture, partly combined with hunting and gathering wild fruits and vegetables in the forest [Luu, 2006; Tran, 2014]. Forests are an inexhaustible source of food and a fundamental and sacred concept to them. “ They are not just space but time; eternity, the realm of infinity ” [Nguyen Ngoc, 2005, p. 64], “ If we live, the forest feeds us, and if we die, we bury in the forest ” [Nguyen, 1994, p. 29]. The group discussions showed that the forest classification according to the ethnic group includes four types: residency forests, production forests, living activity forests, and spiritual forests. Residency forests are where the forests have turned into residential land, where people build villages to settle down and live permanently. Production forests are plots of land where agricultural activities occur ⁶. Living activity forests are places where people can exploit forest resources to serve their lives (collecting raw materials, hunting, and gathering). Sacred forests, also known as the spiritual forests, are where the dead are buried and where the gods reside, and it is not allowed to enter the forests ⁷. Thus, it can see that forests with the above classification thought are present throughout the daily activities of the ethnic group, from the earthly life to spiritual life. Forests become an essential factor in creating a cultural identity for the community [Tran, 2014]. Forests are regarded as entities that live in a positive relationship with people and share all livelihood activities and beliefs. “ It is hard for one to find a cultural expression here that is not related to forests, or rather, does not take a profound relationship between humans and forests as a basis ” [Nguyen Ngoc, 2004, p. 64]. Humans communicate with the forest god and the souls in the forest by giving offerings at sacred sites. The whole community worships and unites based on that “sacredness.” That “sacredness” is a god [Arhem, 2009]. The results of our group dis-

cussions also showed the “presence” of abhui(s) in the types of forests assessed by the members as follows (see table 1).

Presence of the "god-soul" ( abhui ) in different types of forests

Table 1

Types of forests	Level	Note
Spiritual forests	4	Many:  4 Moderate: 3 Few:    2 None:    1
Production forests	3
Living activity forests	3
Residency forests	2

Fieldwork materials in 2018, results of group discussions.

This result shows that the abhui(s) occurs more in spiritual forests, production forests, and living activity forests. And there is less in residency forests. It is consistent with our observations that the concept of abhui carries more bad meanings than good ones. Forests with a lot of abhui are locations where humans do not reside. They are the space beyond human control, so that space contains secrets or natural powers that humans cannot withstand. In the residency forests where people live peacefully, evil souls cannot live. Souls outside the village's social sphere are considered potentially dangerous and harmful [Arhem, 2009]. However, from the concept of such harmful abhui(s) , the Co Tu people have sanctified the whole forest into a great deity called Yang forest .

Yang forest is not as deficient as the majority of abhui in the forest. Yang gives food and shelter to the people. “ Yang is very close to the villagers. Yang is not going far ” (Interview with the woman, 54 years old, in 11/2017). “ Yang always blesses the villagers ” (Interview with the man, 65 years old, in 11/2017). In the worldview of the ethnic group, the concept of Yang refers to supernatural forces within the residential areas of the ethnic group, such as the private houses, the longhouse of the whole family ⁸, or the Guol house ⁹. They are where souls and ancestors reside. These souls always bless the individuals and the village community. Thus, the Co Tu people have tried to impose their knowledge and will on the forest world, in which people have regarded themselves and the forest world as associated entities. The forest is the world of nature but has been sanctified with the world of man. With the mystical powers of the souls -abhui(s) , the Yang forest has become closer to humans, sacred as the best god. Through in-depth interviews and group discussions, we have summarized some images of forest gods in the abstract thinking of the Co Tu people. The gods are identified through many different shapes, with personalities and excellent sources of power and energy. The table of the anthropomorphic images of the forest god can be viewed as follows (see table 2).

Thus, it can be seen that the ethnic group has sanctified forests with close, fierce, and mysterious images. Gods, to some extent, are liberated from individual trees and take the form of human beings, and have extraordinary powers [Frazer, 1923/2007, p. 201]. And regardless of the images, forests always play the role of protecting, determining, and arranging the order for human life. “Birds in the sky need immense green forests. Fish in water need clear water. The Co Tu people need Mother forest’s protection for multiplication and growth of villages, successful crop yields, and the Co Tu people everywhere to live forever. Losing forests, birds no longer sing. Losing streams and rivers, fish no longer breathe. Losing Mother Forest, the Co Tu people will perish,” lyrics in a folk song praising forests shared by a Co Tu village elder (Interview with the man, 65 years old, in 7/2019). Every 2–3 years, the people worship the forest god in the spring to express their gratitude to the forest god for giving the villagers a year of food and peace. This is a big festival: “A poor village should offer a chicken and a pig. A rich village offers a buffalo, organizes folk dances, and plays all day” (Interview with the man, 60 years old, in 11/2018).

Table 2 The images illustrating the appearance of the Yang forest

Illustrated images	Ability / power	Characters
Parents	Protecting, nurturing	Tolerant, understanding
Mother	Protecting, nurturing	Tolerant, understanding
Breast milk	Nurturing, giving food	Tolerant, understanding
Origin of life	Endless power	Quiet, peaceful
Judge	Moving quickly	Transparent, clear
Big old tree	Many miracles	Tranquil, mysterious
Areas with dense foliage, little sunlight	Many miracles	Blessing
The big, fierce animal	Moving fast	Ferocious
Invisible ghost	Moving fast	Mysterious, causing fear
Time	Keeping the past, good and bad memories	Mysterious, profound, causing fear
Ending	Superpower	Mysterious, profound causing fear
The decider of fate	Superpower	Mysterious, causing fear

Fieldwork materials in 2018, results of group discussions and in-depth interviews.

3.2.    Protecting forests is protecting the god: the strictness of the Co Tu customary law on forests

Due to them living in the highland terrain and mountains, forests are the most critical resource for the survival of the Co Tu people. Everything from forests is a means for villages to earn their living from generation to generation. Forest protection is the protection of life resources. And protecting forests is also covering the sacredness of the forests. That sacredness emphasizes the power (souls in the forest) and the significant role of the forests in the life of the Co Tu community. Therefore, in the system of their customary law ¹⁰, the contents of the management and use of forests and forest land occupy a significant proportion [Nguyen, 2001; 2004, Bui, 2020]. It is believed that this customary law has helped create a safe distance between the people and forests. As a convention, that distance personifies the relationship between man and nature, in which the people see forests as entities like themselves, living together in the real world of humans. Group discussions in different age groups all confirmed, “ Forest trees have existed since ancient times and been left by ancestors. Protecting forest trees is protecting ancestors. Protecting forest trees is protecting village community life ”. The power of forests is the “hidden” souls in the trees. Customary law was designed to prevent human acts (whether unintentional or intentional) that could offend the forest souls.

And “ the consequences of the offending are hard to say . It’s not just that individual but the entire community affected. Maybe the god will sow calamities such as epidemics, natural disasters, crop failure. Everything in the forest belongs to the community, not to the individual ” (Interview with the man, 60 years old, in 11/2018). Thus, it can be seen that customary law is in place to ensure the community’s common interests. The customary law exudes the spirit of community cohesion, democracy, and equality among the village members. Customary law shows a profound sense of community [Ngô, 2003]. Protecting forests is protecting the gods, the peace of the community.

In Vietnam, customary law of ethnic groups is divided into three main categories: (1) customary law in the form of oral rhymes; (2) written or documented customary law; (3) customary law in the form of social practices. The customary law of the Co Tu people belongs to the category (3). In the customary law related to forests, there are two contents: forest management, forest and forest land use. Each range is passed down through social practices and clearly expressed through rituals and levels of taboos in production. The following social practice illustrations can be viewed:

• •    For production forests: when desiring to cultivate a particular piece of land, the people must perform the “land request” ritual to notify and ask permission from the souls. Specifically, there are ground soul and tree souls ( abhui earth and abhui(s) tree ). Offerings include wine, chicken, and sticky rice. The head of the family wanting to “request the land” will be the one to perform the rituals. In every step of the farming process, like cleaning and cutting, burning, planting, and harvesting ¹¹, people must carefully observe and make notes to avoid offending the forest souls. For example, when cleaning and cutting, if they encounter trees with strange shapes such as two snakes entwined with each other or find there are many rats in that land, they have to perform a ritual to worship the souls of the land and trees. In this ritual, they use two bamboo sticks to ask for permission; if the result is a face-down and a face-up, the souls accept their request to cut trees. In the burning stage, the customary law stipulates a hefty punishment for letting the fire spread to other plots of land. If the fire spreads to other villages or affects sacred forests, the penalty will be much heavier. The punishment offerings here are wine, white buffalo, and sticky rice.

• •    For living activity forests: the people have a list of trees to pay attention to, from shrubs, soft-bodied vines to tall trees. Each type of tree will have its uses and a regulated level of exploitation and service. For example, woody trees, such as Pomu, Jackfruit, Magnolia Fordiana, can be exploited for timber to build houses and make coffins for dead bodies. Banyan trees and mulberry trees are not to be approached, especially not to be burned. Even for the collection of forest products, the customary law stipulates those leafy plants are not to be over-collected; for fruit plants, when the fruits are taken, they must be replanted; for root plants, the people are not allowed to take all the roots so that the plants can grow. If anyone violates the customary law, the souls will make them sick and exhausted.

• •    For residency forests: The most crucial detail in the people’s respecting and asking for protection from the tree souls is to keep the solemnity of the Guol house – the soul of the village

  [Nguyễn, 2001, p. 328]. The Guol house is usually round at both ends, and in the middle is the main-pillar which usually has a round bottom, a square top and is surrounded by sub pillars and supporting pillars at the two edges. For the Guol house, the pillars play a vital role, symbolizing the image and status of the village patriarch. The bigger and more beautiful the main-pillar is, the more it shows the role of the village patriarch and the strength and position of that village. The main-pillar is usually buried straight into the ground about 1.5 m. The total number of pillars for the house is about 38, of which there are 18 main pillars and 20 sub pillars [Iizuka, 2012, p. 108]. Villagers often use pine wood to make these pillars. There are many rituals to worship the tree souls performed for the stages, from choosing the type of trees for timber to make a pillar, cutting down trees and bringing them to build the Guol house, and inaugurating the Guol house. Every year, the villagers hold a buffalo stabbing festival ¹² at the Guol house to ask for the protection and blessing of the forest god (the souls of the trees) existing in the Guol, in the residential area of the people. The forest god of the natural world has entered the life of the villagers, residing in the pillars of the Guol house; hence the relationship between humans and gods is closer.

• •    For sacred forests: This is the type of forest that is not offended with loud words, curses, or insults, according to the customary law. It is not allowed to offend the souls by indiscriminately cutting down trees, giant trees. “We believe that every time we destroy anything in the sacred forest, we appropriate a soul” (Interview with the man, 75 years old, in 11/2018). If anyone cuts down an old tree, destroying the house of the god, then the god will punish the villagers with all forms of illnesses, diseases, or death. Before approaching or taking anything from the sacred forest, one must offer the soul’s permission. The sacred forest is home to many kinds of tree souls, where the forest’s powers are the strongest level. The space of the sacred forest is also where the forest god worshiping ceremony is held. It is a ritual that clearly shows respect for the tree souls and the highest honor to the forest god.

4.    Conclusion

With the above explanations and analysis, we have precise results that in the ecocosmology the Co Tu people have established their values of belief in tree souls and reverence for the forest god. They have personified tree entities as souls and incorporated these concepts into their lives. They have established a secure relationship between nature and man through the presence of customary law, trying to impose their knowledge and will on the natural world. In the current trend of protecting and preserving the living environment, the concept of trees in the ecocosmology and the constraints and regulations in the customary law system of the people in the management and use of forests and forest land are significant in some respects. Such sanctification of such natural resources as trees and forests is the main reason for the community to deter and educate community members not to cut down, destroy and pollute resources, contributing significantly to protecting the community's livelihoods. “Once humans attach the importance to the existence of gods and do not neglect to pray, the gods will favor them” [Vu, 2004, p. 290]. Clearly, the portrayal of self-image and the natural world as associated inter-subjects through the social conceptions and practices are the meaningful educational and positive incentives in building community awareness of the responsible management, protection, and use of shared resources.

Ho Viet Hoang . Nâng quyền cho các dân tộc thiểu số trong quản lý rừng cộng đồng: Những giá trị rừng tâm linh truyền thống [Empowering ethnic minorities in community forest management: Traditional spiritual forest values]. Tạp chí Khoa học và Công nghệ [ Journal of Science and Technology ], 2016, vol. 4, no. 2, pp. 51–63. (in Viet.)

Iizuka Akiko . Traditional community houses of the Co-tu ethnic group in central Vietnam. SANSAI Journal of GSGES , 2012, no. 6, pp. 97–114.

Ingold Tim . The Perception of the Environment. Essays on livelihood, dwelling and skill. London and New York, Routledge Publ., 2000, 480 p.

Laura Rival. The Social Life of Trees, Anthropological Perspectives on Tree Symbolism. London, Routledge, 1998, 332 p.

Le Anh Tuan . Vai trò của rừng tâm linh trong đời sống của các tộc người thiểu số ở miền núi Trung bộ Việt Nam [The role of the spiritual forest in life of ethnic minorities in the Vietnam's central mountainous area]. Tạp chí Nghiên cứu Tôn giáo [ Religious Studies ], 2016, no. 3 (153), pp. 3–18. (in Viet.)

Luu Hung. Góp phần tìm hiểu văn hóa Cơ tu [Contribution to the study on Co Tu culture]. Social Science Publ., Ha Noi, 2006, 292 p. (in Viet.)

Ngo Duc Thinh. Tìm hiểu luật tục các dân tộc thiểu số ở Việt Nam [Learn the customary law of ethnic groups in Vietnam]. Social Science Publ., Ha Noi, 2003, 590 p. (in Viet.)

Nguyen Huu Thong . Ka Tu-Kẻ sống đầu ngọn nước [Ka Tu-who lives in the watershed]. Thuan Hoa Publ., Hue, 2004, 425 p. (in Viet.)

Nguyen Tri Hung . Truyện kể dân gian Cơ Tu [Co Tu Folk tales]. Da Nang Publ., Da Nang, 1994, 128 p. (in Viet.)

Nguyen Ngoc . Rừng trong văn hóa Tây Nguyên [Forests in Central Highlands culture]. In: Tản mạn và nhớ quên [Roaming & Forgetting]. Arts Publ., Ho Chi Minh, 2005, pp. 61–64. (in Viet.)

Nguyen Van Manh . Luật tục của người Tà ôi, Cơ-tu, Bru-Vân Kiều ở Quảng Trị, Thừa Thiên Huế [Customary law of Ta oi, Co-tu, Bru-Van Kieu in Quang Tri, Thua Thien Hue]. Thuan Hoa Publ., Hue, 2001, 418 p. (in Viet.)

Nurit Bird-David . Tribal metaphorization of human-nature relatedness: A comparative analysis. In: Anthropological Perspectives on Environmentalism. Milton, K. ed. Association of Social Anthropologists Monograph Series. London, Rutledge Publishing, 1993, pp. 112–125.

Tran Nguyen Khanh Phong . Văn học dân gian Cơ Tu [Co Tu ethnic folklore]. Social Sciences Publ., Ha Noi, 2015, 478 p. (in Viet.)

Tran Thi Mai An . Tổ chức xã hội truyền thống của người Cơ-tu ở huyện Nam Đông, tỉnh Thừa Thiên Huế [The traditional social organization of the Co-tu people in Nam Dong District, Thua Thien Hue Province]. Ha Noi, National Political Publ., 2014, 186 p. (in Viet.)

Tylor Edward Burnett . The Origins of Culture [Part I of “Primitive Culture”]. Harper & Row Publ., 1871/1958, 416 p.

Vu Minh Chi . Culture Anthropology: Man with nature, society and the supernatural world. National Political Publ., 2004, 427 p. (in Viet.)