Other mammals have oral sex

http://www.livescience.com/46364-brown-bears-caught-performing-oral-sex.html 

History of oral sex

Tannahill, Reay. Sex in History. Stein and Day, NY, 1980.

Clarke, John R. Roman Sex. Harry N. Abrams, NY 2003.

Doniger, Wendy and Sudhir Kakar. Vatsyayana Kamasutra. Oxford University Press, NY, 2002.

Berkowitz, Eric. Sex and Punishment. Counterpoint Press, Berkeley, CA 2012.

Armstrong, David and Liz Metzger Armstrong. The Great American Medicine Show. Prentice Hall, NY, 1991.

https://mic.com/articles/144460/a-history-of-oral-sex-from-fellatio-s-ancient-roots-to-the-modern-blow-job#.OYjXq0MO7

Women’s insecurities about vaginal odor

Grimley, D.M. et al. “Vaginal Douches and Other Feminine Hygiene Products: Women’s Practices and Perceptions of Product Safety,” Maternal and Child Health (2006) 10:303.

Martino, J.L. and S.H. Vermund. “Vaginal Douching: Evidence for Risks or Benefits to Women’s Health,” Epidemiologic Reviews (2002) 24:109.

Stephens-Davidowitz, S. “Searching for Sex,” New York Times, Jan. 25, 2015.

Deep Throat cost and revenue

https://en.wikipedia.org/wiki/Deep_Throat_(film)

TURP and retrograde ejaculation

http://www.sexhealthmatters.org/did-you-know/turp-prostate-surgery-and-retrograde-ejaculation-did-you-know