1World Health Organization.WHO Laboratory manual for the examination of human semen and sperm-cervical mucus interaction.4th ed.Cambridge:Cambridge University Press,1999.p 7-14.
2Kruger TF,Ackerman SB,Simmons KF,Swanson RJ,Brugo SS,Acosta AA.A quick,reliable staining technique for human sperm morphology.Arch Androl,1987,18:275-277.
3Siege S,Castellan Jr NJ.Nonparametric statistics.New York:Mc Graw Hill,1988.