P. A. Nwafor, E. . Ekpo, E. E. . Udofia, and M. E. . Smith, “Effects of Methanol Extract of <em>Piper umbellatum</em> Leaves on Contraceptive and Sexual Behaviour in Rodents”, NIJOPHASR, vol. 1, no. 2, pp. 1–14, Jul. 2012.