Suzanne G. Frayser, Thomas J. Whitby: Studies in Human Sexuality. A Selected Guide. Libraries Unlimited, Englewood 1995, ISBN 0-585-07138-1, S.144 (books.google.com).
Kar Nilamadhab, Gopal Chandra Kar: Comprehensive Textbook of Sexual Medicine. Jaypee Brothers, Medical Publishers, Neu-Delhi 2005, ISBN 81-8061-405-0, S.456 (books.google.com).
