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WikiPedia: Lịch_sử_thế_giới http://www.ifi.unicamp.br/~ghtc/sources/articles.h... http://print.google.com/print?id=TbiVDVY6mRYC&pg=8... http://vlib.iue.it/history/index.html http://www.actionbioscience.org/evolution/johanson... http://www.indianoceanhistory.org/ http://books.google.com.vn/books?id=0Rh2SSIhT6IC&p... http://books.google.com.vn/books?id=4LPODzLgDVEC&p... http://books.google.com.vn/books?id=jrVW9W9eiYMC&p... http://books.google.com.vn/books?id=yFocMaM49SgC&p... https://blogs.wsj.com/economics/2009/04/22/whats-a...