He Z, Zhao Y, Guo C, Liu Y, Sun M, Liu F, Wang X, Guo F, Chen K, Gao L, Ning T, Pan Y, Li Y, Zhang S, Lu C, Wang Z, Cai H, Ke Y. Prevalence and risk factors for esophageal squamous cell cancer and precursor lesions in Anyang, China: a population-based endoscopic survey. British Journal of Cancer. 2010 Aug 10;103(7):1085–8. doi: 10.1038/sj.bjc.6605843.