Van Gundy, C.E., 1934, Some observations of the Unkar group of the Grand Canyon Algonkian: Grand Canyon Nature Notes, v. 9, p. 338-349.
Van Gundy, C.E.
Grand Canyon Nature Notes, v. 9, p. 338-349.
Stratigraphy, Paleontology, Invertebrate, Unkar Group - Grand Canyon Supergroup - Middle Proterozoic,