Harris, I. D., C. Fronczak, L. Roth, and R. B. Meacham. «Fertility and the Aging Male». Reviews in Urology 13, no. 4 (2011): e184 – 190.
Hermann, M., G. Untergasser, H. Rumpold, and P. Berger. «Aging of the Male Reproductive System». Experimental Gerontology 35, no. 9 – 10 (2000): 1267–1279.
MD, Web. «Teen Boys». Web MD, http://teens.webmd.com/boys/testicles-faq.