[Letter from Harris L. Kempner to Kazimierz Terepeta and Andrzej Paprotny, November 17, 1959], letter, November 17, 1959; (https://texashistory.unt.edu/ark:/67531/metapth1294375/m1/1/: accessed July 16, 2024), University of North Texas Libraries, The Portal to Texas History, texashistory.unt.edu.; .