Tang, Yong-Ping, Ying-Song Wu, Ai-Hua Yin, et al. "Determination of median levels of the free β subunit of human chorionic gonadotropin in women from mainland China using a new time-resolved fluoroimmunoassay" Clinical Chemistry and Laboratory Medicine, 48.1 (2009): 109-114. Retrieved 19 May. 2013, from doi:10.1515/cclm.2010.005

Tang, Y., Wu, Y., Yin, A., et al. (2009). Determination of median levels of the free β subunit of human chorionic gonadotropin in women from mainland China using a new time-resolved fluoroimmunoassay. Clinical Chemistry and Laboratory Medicine, 48(1), pp. 1-146. Retrieved 19 May. 2013, from doi:10.1515/cclm.2010.005

Tang, Yong-Ping, Ying-Song Wu, Ai-Hua Yin, et al. 2009. Determination of median levels of the free β subunit of human chorionic gonadotropin in women from mainland China using a new time-resolved fluoroimmunoassay. Clinical Chemistry and Laboratory Medicine. 48(1): 1-146. Retrieved 19 May. 2013, from doi:10.1515/cclm.2010.005