Little remark: According to the designer (see: http://geekdo.com/thread/94915/mistake-in-the-rio-grande-rul...) the rules for 'Sumerians' are explained wrongly in the Rio Grande Rules, which you seem to have used for this reference sheet. When playing 3 Sumerians in an area you can't take all the tribe cards corresponding to the last played tribe card by your opponent, but only the last card and any identical cards it is stacked upon.
