Tài liệu tham khảo WikiPedia: Tokina http://www.tokina.co.jp http://canon-eos.serveblog.net/geraet/frames/lense... http://www.alllenses.org/brand/tokina http://www.nikonians.org/html/resources/non-nikon_... https://commons.wikimedia.org/wiki/Category:KenkoT...