Sources:
- http://online.infobase.com/HRC/LearningCenter/Details/7?articleId=226386
- http://www.britishmuseum.org/search_results.aspx?searchText=mesopotamia&q=mesopotamia
- http://www.mesopotamia.co.uk/staff/resources/background/bg08/home.html
- http://www.mesopotamia.co.uk/staff/resources/background/bg11/home.html
- http://online.infobase.com/HRC/Search/Details/226286?q=mesopotamia%20economics
- http://www.mesopotamia.co.uk/writing/home_set.html
- http://www.mesopotamia.co.uk/writing/explore/exp_set.html
- http://www.mesopotamia.co.uk/time/home_set.html
- Ancient and Medieval History Online | Infobase
- http://factsanddetails.com/world/cat56/sub363/item1514.html
- http://www.historyonthenet.com/mesopotamians/mesopotamian-merchants-and-traders