Nguyen Trong Bac และ Nguyen Van Sanh. (2015) A generalization of cohen's theorem. Mahidol University:ม.ป.ท.Nguyen Trong Bac และ Nguyen Van Sanh. 2015. A generalization of cohen's theorem. ม.ป.ท.:Mahidol University;Nguyen Trong Bac และ Nguyen Van Sanh. A generalization of cohen's theorem. ม.ป.ท.:Mahidol University, 2015. Print.