1. Pregnancy testing;American Pharmaceutical Association,1986
2. Teenage Pregnancy: The Problem That Hasn’t Gone Away;Alan Guttmacher Institute,1980
3. Trends in adolescent contraception, pregnancy, and childbearing;Baldwin,1983
4. Reliability of urinary pregnancy tests in the diagnosis of ectopic pregnancy;Barnes;J Reprod Med,1985
5. Serial B-subunit human chorionic gonadotropin doubling time as a prognosticator of pregnancy outcome in an infertile population;Batzer;Fertil Steril,1981