1. Leighton, M., Seal, U. S., Soemarma, K. et al. 1995. Orangutan life history and vortex analysis. In The Neglected Ape, ed. R. D. Nadler, B. M. F. Galdikas, L. K. Sheeran & N. Rosen. New York, NY: Plenum Press, pp. 97–107
2. MacKinnon, J. R. 1979. Reproductive behaviour in wild orangutan populations. In The Great Apes, ed. D. A. Hamburg & E. R. McCown. Menlo Park, CA: Benjamin/Cummings, pp. 256–73
3. Rijksen, H. D. 1978. A Fieldstudy on Sumatran Orang Utans (Pongo pygmaeus abelii Lesson 1827). Wageningen: H. Veenman & B. V. Zonen
4. ?Alternative? mating behavior in the swordtails Xiphophorus nigrensis and Xiphophorus pygmaeus (Pisces: Poeciliidae)
5. Application of organization-activation theory to alternative male reproductive strategies: a review;Moore;Hormones and Behavior,1991