Suárez VJ, Zavala R, Ureta JM, Hijar G, Lucero J, Pachas P. Effect of levonorgestrel in the ovulation, endometrium, and spermatozoa for emergency oral contraception. Rev Peru Med Exp Salud Publica. 2010;27(2). doi:10.17843/rpmesp.2010.272.1468