Oklahoma Steam Threshers Association
- Pawnee, OK-based group preserving Oklahoma's rich heritage of the early threshing days of the early 1900's; steam traction engines and other old iron.
- http://www.oklahomathreshers.org/

The March of Machines
- Official site of Pawnee-based Oklahoma Steam Threshers Association, dedicated to preserving Oklahoma's heritage of the threshing days of the early 1900s. Steam traction engines and other old iron.
- http://marchofmachines.com/

Oklahoma Historical Society
- Preserving Oklahoma's rich history.
- http://www.ok-history.mus.ok.us/