0.47 T. J. Wilkinson J. H. Christiansen J. Ur M. Widell M. Altaweel, Urbanization within a Dynamic Environment: Modeling Bronze Age Communities in Upper Mesopotamia, American Anthropologist, 2007.

{ population agricultural land agriculture }	0.47
{ university press american pp }	0.13
{ maya political state late }	0.10
{ number data group table }	0.09