1. Ectopic gestation;McElin;Obstet Gynecol Annu,1976
2. Risk factors for ectopic pregnancy;Ankum;Fertil Steril,1996
3. Incidence, epidemiology, risk factors, and etiology;Cartwright,1993
4. The contralateral corpus luteum—an important factor in ectopic pregnancies;Berlind;Obstet Gynecol,1960
5. Current factors in the causation of tubal pregnancy;Kleiner;Am J Obstet Gynecol,1967