1. The diagnosis of ectopic pregnancy: the value of the hCG discriminatory zone;Romero;Obstet Gynecol,1985
2. A method of screening for ectopic pregnancy and its indications;Kadar;Obstet Gynecol,1981
3. Beta-hCG as a diagnostic aid for suspected ectopic pregnancy;Schwartz;Obstet Gynecol,1980