Karlstrom, Karl, and Laura Crossey. “Classic Rock Tours 3. Grand Canyon Geology, One Hundred and Fifty Years After John Wesley Powell: A Geology Guide for Visiting the South Rim of Grand Canyon National Park”. Geoscience Canada, vol. 46, no. 4, Dec. 2019, pp. 163-9, doi:10.12789/geocanj.2019.46.153.