The geological history and evolution of the horse / by Elmer S. Riggs, Assoc. Curator of Paleontology.

no.13(1932)

A new and primitive early Oligocene horse from Trans-Pecos Texas / Paul O. McGrew, Dept. of Geology, The University of Wyoming.

v.10:no.15(1953)

Model of an Arizona gold mine.

no.1(1922)