- http://dictionary.reference.com/browse/physical+geography
- https://www.boundless.com/sociology/textbooks/boundless-sociology-textbook/culture-3/culture-and-society-29/cultureal-universals-184-5913/
- http://dictionary.reference.com/browse/government
- www.examples.yourdictionary.com
- http://dictionary.reference.com/browse/economic?&o=100074&s=t
- http://dictionary.reference.com/browse/prehistory?s=t
- http://ngkids.co.uk/history/ten-facts-about-ancient-egypt
- http://www.ducksters.com/history/china/ancient_china.php
- www.primaryhomeworkhelp.co.uk/Greece.html
- www.squizzes.com/ancient-egypt-fast-facts
- egypt.mrdonn.org/government/html
- egypt.mrdonn.org/trade.html
- http://en.wikipedia.org/wiki/Terracotta_Army
- www.ducksters.com/history/china/ancient_china.php
- cinderellamoon.com
- http://www.historyforkids.org/learn/china/economy/
- http://www.ancient.eu/Mesopotamia/
- www.softschools.com/facts/ancient/civilizations/mesopotamia/facts/876/
- gatewaystobabylon.com
- http://mesopotamia.mrdonn.org/school.html
- www.ancientmesopotamians.com/ancient-mesopotamia-money-and-currency.html
- www.ancientgreece.com/s/olympics
- http://classroom.synonym.com
- http://classroom.synonym.com/things-sold-traded-ancient-greece-18795.html
- http://www.historyforkids.org/learn/greeks/economy/coins.htm#!