1. Brain Gender
2. American Psychological Association Answers to your questions about transgender people, gender identity, and gender expression Washington, DC 2011 http://www.apa.org/topics/lgbt/transgender.aspx
3. American Psychological Association Answers to your questions: For a better understanding of sexual orientation and homosexuality Washington, DC 2008 http://www.apa.org/topics/lgbt/orientation.pdf
4. Sex determination and gonadal development in mammals;Wilhelm;Physiol Rev,2007