Ancient civilizations in much of Mexico and Central America were making different grades of rubber 3,000 years before Charles Goodyear "stabilized" the stuff in the mid-19th century, new research ...
[Part 1] Aztec -- 1. The historical and geographical background of the Aztecs -- 2. The people -- 3. The Aztec "kings" and the directing classes -- 4. The achievements -- [Part 2] Maya -- 1. This ...
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