"The optimized cascade process" by H. W. Barber and S. J. Orloski in Oil and Gas Journal, April 17, 1972, Box: 19, Folder: 58. Charles Heller papers, RH MS 314. University of Kansas. Kenneth Spencer Research Library. https://archives.lib.ku.edu/repositories/3/archival_objects/492892 Accessed April 19, 2024.