J. S. MAK, A. Y. WONG, J. Y. WONG, and P.-K. HUI, “A Cross-sectional Study of the Relationship of Serum Folic Acid, Vitamin B12, Zinc, Magnesium with Semen Parameters in Infertile Couples in Hong Kong”, Hong Kong J Gynaecol Obstet Midwifery, vol. 15, no. 2, Jul. 2015.