World supply - "The changing pattern and its implications for natural gas and fetilizer situation east of the Suez Canal" by Walter Levy, 1962, Box: 19, Folder: 39. Charles Heller papers, RH MS 314. University of Kansas. Kenneth Spencer Research Library. https://archives.lib.ku.edu/repositories/3/archival_objects/492865 Accessed May 05, 2024.