[Letter from Isaac H. Kempner to Clarence J. Ziegler, September 23, 1960], letter, September 23, 1960; (https://texashistory.unt.edu/ark:/67531/metapth1480865/m1/1/: accessed July 16, 2024), University of North Texas Libraries, The Portal to Texas History, texashistory.unt.edu.; .