Mohamed A. M. Hassan, M.Sc., and Stephen R. Killick, M.D. Effect of male age on fertility: evidence for the decline in male fertility with increasing age. Fertility & Sterility, 2003, 79 (suppl 3):1520-1527.
 Qian-Xi Zhu, Catherine Meads, Min-Li Lu, et al., Turning point of age for semen quality: a population-based study in Chinese men. Fertility & Sterility, 2011, 96 (3): 572-576.
 Jimei Cong, Pingping Li, Liqiang Zheng, Jichun Tan. Prevalence and risk factors of infertility at a rural site of northern China. PLOS ONE DOI: 10.1371 /journal. pone. 0155563 May 13, 2016
 Z Zhou, D Zheng, H Wu,et al., Epidemiology of infertility in China: a population-based study. BJOG 2017, DOI: 10.1111/1471-0528.14966.