Increasing prevalence of myopia and the impact of education in primary-school students in Xi'an, north-western of China oleh Lu Ye, Lu Ye, Yan-qi Yang, Guo-yun Zhang, Wen-jun Wang, Mei-xia Ren, Pan Ge, Jian Zhang, Nan Zhang, Xing-zhou Liu, Ming-lei Zhang, Yu-jiao Tong, Liang-cai Lu, Mo-qi Lv, Dang-xia Zhou, Cheng Pei