Books:
Bagemihl, Bruce: Biological Exuberance: Animal Homosexuality and Natural Diversity (Stonewall Inn Editions)
Long, John A:The Dawn of the Deed: The Prehistoric Origins of Sex
Long, John A: Hung Like an Argentine Duck: A Journey Back in Time to the Origins of Sexual Intimacy
Roughgarden, Joan: Evolution’s Rainbow: Diversity, Gender, and Sexuality in Nature and People
Sommer, Volker and Vasey, Paul: Homosexual Behaviour in Animals: An Evolutionary Perspective