Kempner, Isaac H. (Isaac Herbert), 1873-1967. [Letter from Isaac H. Kempner to Irving M. Engel, April 30, 1957], letter, April 30, 1957; (https://texashistory.unt.edu/ark:/67531/metapth1512771/m1/2/: accessed July 18, 2024), University of North Texas Libraries, The Portal to Texas History, texashistory.unt.edu.; .