Essential Concepts for Healthy Living. Jones & Bartlett Publishers, 2012 — 180–181-bet. ISBN 978-1-4496-3062-1. „Most heterosexuals are familiar with the notion of 'having sex' or sexual intercourse as vaginal sex, the insertion of a penis into a vagina. Vaginal sex, or coitus, is the most common and popular form of intimate sexual activity between partners.“
„Sexo oral e risco do HIV“. Centers for Disease Control and Prevention (CDC) (junho de 2009). 2013-yil 10-mayda asl nusxadan arxivlangan. Qaraldi: 30 de agosto de 2013.
Sexual intercourse most commonly means penile–vaginal penetration for sexual pleasure or sexual reproduction; dictionary sources state that it especially means this, and scholarly sources over the years agree. See, for example;
„Copulation“. Dorland's Medical Dictionary for Health Consumers, 2007/TheFreeDictionary.com para definições gramaticais. Qaraldi: 6 de setembro de 2012.
„Sexo oral e risco do HIV“. Centers for Disease Control and Prevention (CDC) (junho de 2009). 2013-yil 10-mayda asl nusxadan arxivlangan. Qaraldi: 30 de agosto de 2013.
