"Crude oil: demands and supply of crude oil projection" by Ad hoc panel of experts and "Cost of crude petroleum production: trends and prospects" by Paul G. Bradley, 1971 - 1972, Box: 23, Folder: 15. Charles Heller papers, RH MS 314. University of Kansas. Kenneth Spencer Research Library. https://archives.lib.ku.edu/repositories/3/archival_objects/493210 Accessed April 18, 2024.