Both these books appear to be very popular in Elementary schools, at least in my area and are available a many local libraries. Check them out at: https://www.worldcat.org
Kepis and turkey calls : an anthology of the War between the States in Indian territory
Author: Mark Lea Cantrell; Mac R Harris
Publisher: Oklahoma City : Western Heritage Books, 1982.
Includes material on the battles of Chustenahlah, Pea Ridge, Honey Springs, Barren Creek, and Cabin Creek. Also includes material on the activities of William Clarke Quantrill and African-American troops in Indian Territory during the Civil War.
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Indian cavalry in Confederate service; being a brief account of Confederate organization and operation of Indian troops in Indian Territory, 1861-1865, and containing excerpts from the official records of General Albert Pike.
Author: Albert Pike; Thomas Gilcrease Institute of American History and Art.
Publisher: [Tulsa], [©1965]
Series: American scene magazine, 6, no. 1.