Aveling, R. J. (1982). Orang utan conservation in Sumatra, by habitat protection and conservation education. In L. E. M. de Boer (Ed.), The orang utan: Its biology and conservation, pp. 299-315. The Hague: Dr. W. Junk Publishers.

Aveling, R. J., & Mitchell, A. (1982). Is rehabilitating orangutans worthwhile? Oryx, 16, 263-271.

Bennett, J. M. (1991). Orangutans in Sarawak: Past, present, and future. In Proceedings on the Conservation of Great Apes in the New World Order of the Environment, pp. 87-94. Republic of Indonesia Ministries of Forestry and Tourism, Post, and Telecommunication.

de Silva, G. S. (1965). The East-coast Experiment. IUCN Public N.S. 10: Conservation in tropical South East Asia, Bangkok, 229-302.

Frey, R. (1978). Management of orangutans. In Wildlife management in Southeast Asia, pp. 199-215.

Galdikas, B., & Brindamour, R. (1975). Orangutans, Indonesia’s "people of the forest." National Geographic, 148, 444-473.

Galdikas, B. M. F., & Shapiro, G. L. (1994). A guidebook to Tanjung Puting National Park, Kalimantan Tengah (Central Borneo). Jakarta: PT Gramedia Putaka Utama and the Orangutan Foundation International.

Harrisson, B. (1962). The immediate problem of the orangutan. The Malayan Nature Journal, 16, 4-5.

IBN-DLO (Institute of Forestry and Nature Research of the Netherlands). (1995). The Meratus Rainforest Project: Conservation of Rainforest and Orang utans in Southeast Kalimantan, Indonesia. Unpublished report.

Kaplan, G. & Rogers, L. (1994). Orang-Utans in Borneo. Armidale, NSW, Australia: University of New England Press.

Lardoux-Gilloux, I. (1994). Rehabilitation centres: Their struggle, their future. In J. J. Ogden, L. A. Perkins, & L. Sheehan (Eds.), Proceedings of the International Conference on "Orangutans: the Neglected Ape." San Diego: Zoological Society of San Diego.

McGreal, S. (1992). Semengoh orangutan rehabilitation centre. IPPL News, 19(3), 21.

Payne, J., & Andau, P. (1989). Orang-Utan: Malaysia's mascot. Kuala Lumpur: Berita Publishing Sdn. Bhd.

Rijksen, H. D. (1978). A field study of Sumatran orang utans (Pongo pygmaeus abelii, Lesson 1872), Ecology, behavior, and conservation. Wageningen, the Netherlands, Mededlingen Landbouwhogeschool: H. Veenman and Zonen B. V.

Rijksen, H. D. (1982). How to save the mysterious "man of the forest"? In L. E. M. de Boer (Ed.), The orang utan: its biology and conservation, pp. 317-341. The Hague: Dr. W. Junk Publishers.

Schaller, G. B. (1961). The orangutan in Sarawak, Zoologica, 46, 73-82.

Smits, W. T. M., Heriyanto, & Ramono, W. (1994). A new method of rehabilitation of orangutans in Indonesia: A first overview. In J. J. Ogden, L. A. Perkins, & L. Sheehan (Eds.), Proceedings of the International Conference on "Orangutans: The Neglected Ape" pp. 29-40. San Diego: Zoological Society of San Diego.

Westermann, J. H. (1936-38). Nature in Zuid and Oost Borneo. In 3 jaren Indisch Nature leven, 11 e jaar verslag (1936-1938). Ne. Ind. Vereeniging tot Natuurbescherming, Batavia: 334-411.