1. Coital frequency and infertility: which male factors predict less frequent coitus among infertile couples? 
Nathan Perlis, M.D., Kirk C. Lo, M.D., Ethan D. Grober, M.D., Leia Spencer, R.N., Keith Jarvi, M.D. 
Fertility and Sterility 
Volume 100, Issue 2, Pages (August 2013)
DOI: /j.fertnstert
Copyright © 2013 American Society for Reproductive Medicine Terms and Conditions

2. Figure 1
Self-reported monthly coital frequency for men presenting to male infertility clinic for consultation.
Fertility and Sterility  , DOI: ( /j.fertnstert )
Copyright © 2013 American Society for Reproductive Medicine Terms and Conditions