Sigman M, Lipshultz LI, Howards SS. Office evaluation of the subfertile male. In Lipshultz LI, Howards SS, Niederberger CS, eds. Infertility in the male, 4th ed. New York:Cambridge University Press 2009;153-76.
Gnoth C, Godehardt D, Godehardt E, et al. Time to pregnancy: results of the German prospective study and impact on the management of infertility.Hum Reprod. 2003;18:1959-66.