Yi และ Wang Guo. (1994) Contraceptive method choice in three villages in Suburban Beijing. Mahidol University,:ม.ป.ท.Yi และ Wang Guo. 1994. Contraceptive method choice in three villages in Suburban Beijing. ม.ป.ท.:Mahidol University,;Yi และ Wang Guo. Contraceptive method choice in three villages in Suburban Beijing. ม.ป.ท.:Mahidol University, 1994. Print.