Olson, Everett C.; Beerbower, James R. (1953). "The San Angelo Formation, Permian of Texas, and Its Vertebrates". The Journal of Geology. 61 (5): 389–423. Bibcode:1953JG.....61..389O. doi:10.1086/626109.
Olson, Everett C.; Beerbower, James R. (1953). "The San Angelo Formation, Permian of Texas, and Its Vertebrates". The Journal of Geology. 61 (5): 389–423. Bibcode:1953JG.....61..389O. doi:10.1086/626109.