Olson, E.C. (1989)
The Arroyo Formation (Leonardian: Lower Permian) and Its Vertebrate Fossils. Texas Memorial Museum Bulletin, 35: 30pp

Olson, E.C. & Beerbower, J.R. (1953)
The San Angelo Formation, Permian of Texas, and Its Vertebrates. Journal of Geology, 61(5), 389–423

Olson, E.C. (1946)
Fresh- and brackish-water vertebrate-bearing deposits of the Pennsylvanian of Illinois. The Journal of Geology, 54(5), 281–305
DOI: 10.1086/625364