3Tomas C, Orava M, Tuomivaara OL, Martikainen H. Low pregnancy race is achieved in patients treated with intracytoplasmic sperm injection due to previous low or failed fertilization in in-vitro fertilization. Hum Reprod 1998,132:65～70.
4Palena G,Joris H,Deveroeg P,et al. Pregnancies after intracytoplasmic sperm injection of single spermatozoon into an oocyte. Lancet, 1992,340: 17-18.
5Kupker. Pregnancy outcome after assisted fertilization-a short surgcry. Intcrnational Journal of Andrology, 1997,20(suppl 3): 65-68.
6In van seirteghem A, Devroey Pand, Liebaers (eds). Genetics and Assisted Human conception. Oxford University Press. Oxford Pp, 160-176.
