La Pera, G., F. De Luca, A. Guerani, A. Palmieri, and G. Franco. “Prevalence of Phimosis and Foreskin Sliding Abnormalities in Male Adolescents and Their Correlation With Later Onset of First Sexual Intercourse”. Archivio Italiano Di Urologia E Andrologia, vol. 89, no. 4, Dec. 2017, pp. 310-2, doi:10.4081/aiua.2017.4.310.