Fertilizer - "A study of the establishment of nitrogenous fertilizer production" by R. P. Cook and V. Rao Vangala, 1975, Box: 21, Folder: 20. Charles Heller papers, RH MS 314. University of Kansas. Kenneth Spencer Research Library. https://archives.lib.ku.edu/repositories/3/archival_objects/493104 Accessed November 28, 2024.