1. Ectopic pregnancy: changes in serum human chorionic gonadotropin concentration;Cartwright;Obstet Gynecol,1984
2. A contemporary approach to suspected ectopic pregnancy with use of quantitative and qualitative assays for the B-subunit of human chorionic gonadotropin and sonography;Holman;Am J Obstet Gynecol,1984
3. A method of screening for ectopic pregnancy and its indication;Kadar;Obstet Gynecol,1981
4. Discriminatory hCG zone: its use in the sonographic evaluation for ectopic pregnancy;Kadar;Obstet Gynecol,1981
5. Diagnosis of ectopic pregnancy: value of the discriminatory hCG zone;Romero;Obstet Gynecol,1985