BAGEMIHL, Bruce. Biological exuberance : animal homosexuality and natural diversity. New York : St. Martin's Press, 1999. xv, 751 s. Stonewall Inn editions. Available on Internet: <http://www.loc.gov/catdir/bios/hol054/98028528.html> <http://www.loc.gov/catdir/description/hol042/98028528.html> ISBN 978-0-312-25377-6.