Genetic heterogeneity of oesophageal cancer in high-incidence areas of southern and northern China. oleh Zhang Guohong, Su Min, Wang Duenmei, Hu Songnian, Liu Min, Li Jinsong, Lin Hongbin, Zhang Feng, Tian Dongping, Yang Heling, Liu Zhicai, Lian Shiyong, Guo Quansheng, Li Xiaoyun, Gao Yuxia