Gilbert, W.G., 1991, Bedrock geology of the eastern Gila Bend Mountains, Maricopa County, Arizona [Cotton Center, Citrus Valley East, Cotton Center NW, and Spring Mtn. 7.5 min]: Arizona Geological Survey Open-File Report 91-05, 13 p., 1 sheet, scale 1:24,000. Location: Gila Bend Mts.,