Runnels, Russell T.; Kulstad, Robert O.; McDuffee, Clinton; Schleicher, John A. (1952). "Oil Shale in Kansas". Kansas Geological Survey Bulletin (96, part 3). University of Kansas Publications. Retrieved 2009-05-30.
"About Oil Shale". Shale Oil Information Center, Inc. Retrieved 2007-07-28.
state.co.us
geosurvey.state.co.us
"Oil shale—enormous potential but...?"(PDF). RockTalk. 7 (2). Division of Minerals and Geology of Colorado Geological Survey. April 2004. Archived from the original(PDF) on 2007-07-13. Retrieved 2007-07-28.
"Oil shale—enormous potential but...?"(PDF). RockTalk. 7 (2). Division of Minerals and Geology of Colorado Geological Survey. April 2004. Archived from the original(PDF) on 2007-07-13. Retrieved 2007-07-28.