Karl E. Karlstrom, John P. Lee, Shari A. Kelley, Ryan S. Crow, Laura J. Crossey, Richard A. Young, Greg Lazear, L. Sue Beard, Jason W. Ricketts, Matthew Fox, David L. Shuster,
Formation of the Grand Canyon 5 to 6 million years ago through integration of older palaeocanyons Nature Geoscience. ,vol. 7, pp. 239- 244 ,(2014) ,
10.1038/NGEO2065