[Letter from Harris L. Kempner to Dr. Marion J. Levy, Jr., April 1, 1964], letter, April 1, 1964; (https://texashistory.unt.edu/ark:/67531/metapth1421096/m1/2/: accessed July 9, 2024), University of North Texas Libraries, The Portal to Texas History, texashistory.unt.edu.; .