"The Evolution: the state of the oil industry" by Dr. P. H. Frankel and W. L. Newton (1960); "Prospects of the international petroleum industry" by P. H. Frankel (UN seminar, 1962); "Prospects of the evolution of the world petroleum industry" by P. H. Frankel (1973); "World oil in transition" by Walter J. Levy (The Economist, 1961); "Petrochemical industries 1967 and later" by Peter W. Sherwood (World Petroleum, April 1967), Box: 20, Folder: 4. Charles Heller papers, RH MS 314. University of Kansas. Kenneth Spencer Research Library. https://archives.lib.ku.edu/repositories/3/archival_objects/492908 Accessed May 01, 2024.