[1], Marvalee H. Wake (15 September 1992). Hyman’s Comparative Vertebrate Anatomy. University of Chicago Press. p. 583. ISBN 978-0-226-87013-7. Nuoroda tikrinta 6 May 2013.
[2], Roughgarden, Joan (2004). Evolution’s Rainbow: Diversity, Gender, and Sexuality in Nature and People. University of California Press. p. 38. ISBN 978-0-520-24073-5. Nuoroda tikrinta 17 October 2013.
[3], Dixson, Alan F. (26 January 2012). Primate Sexuality: Comparative Studies of the Prosimians, Monkeys, Apes, and Humans. Oxford University Press. p. 364. ISBN 978-0-19-954464-6. Nuoroda tikrinta 17 October 2013.
