Evans, R.O.; et al. (March 1997). "Center Pivot and Linear Move Irrigation System"(PDF). North Carolina Cooperative Extension Service, North Carolina State University. Archived from the original(PDF) on October 21, 2012. Retrieved June 6, 2012.
Rainwater, Ken (January 1, 2004). "Book Review: The Future of the Southern Plains". Great Plains Quarterly Great Plains Studies. Lincoln, Nebraska: Center for Great Plains Quarterly Great Plains Studies, University of Nebraska.
Evans, R.O.; et al. (March 1997). "Center Pivot and Linear Move Irrigation System"(PDF). North Carolina Cooperative Extension Service, North Carolina State University. Archived from the original(PDF) on October 21, 2012. Retrieved June 6, 2012.