^Nola Cooke, Tana Li, James Anderson - The Tongking Gulf Through History - Page 46 2011 -"Nishimura actually suggested the Đông Sơn phase belonged in the late metal age, and some other Japanese scholars argued that, contrary to the conventional belief that the Han invasion ended Đông Sơn culture, Đông Sơn artifacts, ..."
^Vietnam Fine Arts Museum 2000 "... the bronze cylindrical jars, drums, Weapons and tools which were sophistically carved and belonged to the World famous Đông Sơn culture dating from thousands of years; the Sculptures in the round, the ornamental architectural Sculptures...."