Gilbert, G.K., 1893, From Flagstaff to the Grand Canyon, in Emmons, S.F., ed., Geological guide book of the Rocky Mountain excursion, Congres Geologique International, Compte Rendu de la 5me Session, Washington, 1891: Washington, Imprimerie du Gouvernement [U.S. Government Printing Office], Part 4B, p. 472-473.
