Schmidt Webb et al. 1998. Schmidt, John C.; Webb, Robert H.; Valdez, Richard A.; Marzolf, G. Richard; Stevens, Lawrence E. Science and Values in River Restoration in the Grand Canyon. BioScience. September 1998, 48 (9): 735–747. JSTOR 1313336. doi:10.2307/1313336.
Schmidt Webb et al. 1998. Schmidt, John C.; Webb, Robert H.; Valdez, Richard A.; Marzolf, G. Richard; Stevens, Lawrence E. Science and Values in River Restoration in the Grand Canyon. BioScience. September 1998, 48 (9): 735–747. JSTOR 1313336. doi:10.2307/1313336.