Agricultural Mechanization in Asia, Africa and Latin America. 31 (3): 59. ↑ Matsumura, Hirofumi; Cuong, Nguyen Lan; Thuy, Nguyen Kim; Anezaki, Tomoko (2001). "Dental Morphology of the Early Hoabinian, the Neolithic da but and the Metal Age Dong Son Civilized Peoples in Vietnam".