James M. Robertson and Ronald F. Broadhead, project directors ; Anthony W. Gorody, contract manager, Gas Research Institute ; Carol A. Hjellming, project editor
by Geoffrey S. Plumlee ... [and others] ; prepared by the U.S. Geological Survey and the Colorado Geological Survey in cooperation with the U.S. Bureau of Land Management
by Belinda F. Arbogast ... [and others] ; prepared in cooperation with the Colorado Geological Survey for the United States Department of Agriculture Forest Service