https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5735067/
http://www.cirp.org/library/disease/STD/fleiss3/
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2596734/
https://www.urotoday.com/conference-highlights/aua-2017/aua-2017-sexual-function/95986-aua-2017-nhanes-nearly-half-of-us-men-test-positive-for-hpv-yet-vaccination-rates-lag-and-recommendations-demur.html