LUI, Kwai-Ying, Yun-Ting LEE, Chun-Hong SO, and Ellen LM YU. 2017. “Difference in Serum Human Chorionic Gonadotrophin Levels Measured Using the World Health Organization 3rd Versus 5th International Standard: A Correlation Study With Reference to Management of Pregnancy of Unknown Location”. Hong Kong Journal of Gynaecology, Obstetrics and Midwifery 17 (1). https://doi.org/10.12809/hkjgom.17.1.219.