McKeel, B. K.; Love, J. D. & Crew, M. E. North-South Cross Section, Pumpkin Buttes, Wyoming, map, January 1973; (https://digital.library.unt.edu/ark:/67531/metadc957876/m1/1/: accessed October 22, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; .