Xie Zhi-Tao, Wang Shen, Zhang Yong-Tao, Tian Zai-Jie, Ma Zhi-Lin, Liu Bo-Yu, and Niu Jing. “The High Prevalence of Knee Osteoarthritis in North China Population: The Handan Osteoarthritis Study”. International Journal of Innovative Research in Medical Science, vol. 2, no. 09, Sept. 2017, p. 1276 to 1279, doi:10.23958/ijirms/vol02-i09/07.