A prospective cohort study on the association between waterpipe tobacco smoking and gastric cancer mortality in Northern Vietnam oleh Hung Xuan Le, Dung Thi Thuy Truong, Long Bao Tran, Phuoc Hong Le, Binh Uyen Duong Pham, Koji Wada, Shunya Ikeda, Ariuntuul Garidkhuu, Can Van Phan, Ngoan Tran Le