1. Cunningham, F.G., MacDonald, P.C., Gant, N.F., Levon, K.J., Gilstrap, L.C. III: Pregnancy. In: Cunningham, F.G., MacDonald, P.C., Gant, N.F., Levon, K.J., Gilstrap, L.C. III (eds.) William Obstetrics, 19th edn. pp. 11–56. CT Appleton Large, Norwalk (1993)
2. Vattanaviboon, P.: Pregnancy test. J. Med. Tech. Assoc. Thai. 25(1), 19–25 (1997)
3. Dunnihoo, D.R.: Test for pregancy. In: Dunnihoo, D.R. (eds.) Fundamentals of Gynecology and Obstetrics, 1st edn. pp. 262–263. Lippinncott, Philadelphia (1990)
4. Kin, P.T., Wee, A., Dan, L., Guo, J.: Diagnostic test – O & G/Pregnancy. In: Kin, P.T., Wee, A., Dan, L., Guo, J. (eds.) MIMS Medex 97, 1st edn, pp. 145–146. Medi & Media, Bangkok (1997)
5. Chard, T.: Pregnancy tests: a review. Hum. Reprod. 7, 701–710 (1992)