Brand, J. P. (1956) Triassic System, in Eastern Llano Estacado and adjoining Osage Plains: West Texas Geol. Soc. and Lubbock Geol. Soc., Guidebook, Spring Field Trip, April 6-7, 1956, pp. 8-9.

Cummins, W. F. (1890) The Permian of Texas and its overlying beds: Texas Geol. Survey 1st Ann. Rept. (1889), pp. 183-197.

—— (1893) Notes on the geology of northwestern Texas: Texas Geol. Survey 4th Ann. Rept. (1892), pt. 1, pp. 177-238.

Drake, N. F. (1892) Stratigraphy of the Triassic formations of northeast Texas: Texas Geol. Survey 3rd Ann. Rept. (1891), pp. 225-247.

Evans, G. L. (1949) Upper Cenozoic of the High Plains: West Texas Geol. Soc. and New Mexico Geol. Soc., Guidebook for Field Trip No. 2, November 9, 1949, pp. 1-9.

*——, and Meade, G. E. (1945) Quaternary of the Texas High Plains, in Contributions to Geology, 1944: Univ. Texas Pub. 4401, pp. 485-507.

*Frye, J. C., and Leonard, A. B. (1957) Studies of Cenozoic geology along eastern margin of Texas High Plains, Armstrong to Howard counties: Univ. Texas, Bur. Econ. Geol. Rept. Inves. No. 32, 62 pp.

*——, and —— (1959) Correlation of the Ogallala Formation (Neogene) in western Texas with type localities in Nebraska: Univ. Texas, Bur. Econ. Geol. Rept. Inves. No. 39, 46 pp.

*——, and —— (1964) Relation of Ogallala Formation to the southern High Plains in Texas: Univ. Texas, Bur. Econ. Geol. Rept. Inves. No. 51, 25 pp.

*Girard, R. M. (1959) Bibliography and index of Texas geology: Univ. Texas Pub. 5910, 238 pp.

*—— (1964) Texas rocks and minerals: Univ. Texas, Bur. Econ. Geol. Guidebook No. 6, 109 pp.

Gould, C. N. (1902) The geology and water resources of the eastern portion of the Panhandle of Texas: U. S. Geol. Survey Water-Supply Paper 154, 64 pp.

—— (1907) The geology and water resources of the western portion of the Panhandle of Texas: U. S. Geol. Survey Water-Supply Paper 191, 70 pp.

*Matthews, W. H., III (1960) Texas fossils: An amateur collector’s handbook: Univ. Texas, Bur. Econ. Geol. Guidebook No. 2, 123 pp.

*Patton, L. T. (1923) The geology of Potter County [Texas]: Univ. Texas Bull. 2330, 180 pp.

*Reed, L. C., and Longnecker, O. M. (1932) The geology of Hemphill County, Texas: Univ. Texas Pub. 3231, 98 pp.

*Sellards, E. H., Adkins, W. S., and Plummer, F. B. (1933) The geology of Texas, Vol. I, Stratigraphy: Univ. Texas Bull. 3232 (August 22, 1932), 1007 pp.

West Texas State University Geological Society (1964) Palo Duro Field Trip Guidebook: West Texas State Univ. Geol. Soc., Canyon, 18 pp.

—— (1960) Geology of Palo Duro Canyon State Park and the Panhandle of Texas: West Texas State Univ. Geol. Soc., Guidebook for 1966 SASGS Annual Field Trip, April 15-17, 1966, 58 pp.

Smith, A. R. (1967) Caves of Palo Duro Canyon: The Texas Caver, Abilene, Texas, vol. 12, pp. 145-148.