• [Wiki] http://en.wikipedia.org/wiki/Pongo_pygmaeus.
• [AnAge] http://genomics.senescence.info/species/entry.php?species=Pongo_pygmaeus.
• [ADW] http://animaldiversity.ummz.umich.edu/accounts/Pongo_pygmaeus/.
• [BondBloc1982] Bond, M. R. and Block, J. A. (1982). Growth and development of twin orang-utans. International Zoo Yearbook, 22(1):256–261. doi:10.1111/j.1748-1090.1982.tb02045.x.
• [Kooy2010] Kooijman, S. (2010). Dynamic Energy Budget theory for metabolic organisation. Cambridge Univ. Press, Cambridge.