educ.psu.edu: The sumerian city-stateArkiveret 4. juni 2009 hos Wayback Machine Citat: "...The people who established the world's first civilization around 3500 B.C. in southern Mesopotamia were known as the Sumerians. The Sumerians learned to control the Tigris and Euphrates Rivers by constructing levees and irrigation canals. As a result, a stable food supply existed, and the Sumerian villages evolved into self-governing city-states..."
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educ.psu.edu: The sumerian city-stateArkiveret 4. juni 2009 hos Wayback Machine Citat: "...The people who established the world's first civilization around 3500 B.C. in southern Mesopotamia were known as the Sumerians. The Sumerians learned to control the Tigris and Euphrates Rivers by constructing levees and irrigation canals. As a result, a stable food supply existed, and the Sumerian villages evolved into self-governing city-states..."
