Kempner, Isaac H. (Isaac Herbert), 1873-1967. [Letter from I. H. Kempner to Dr. C. U. Clark, July 1, 1957], letter, July 1, 1957; (https://texashistory.unt.edu/ark:/67531/metapth1512920/m1/1/: accessed June 24, 2024), University of North Texas Libraries, The Portal to Texas History, texashistory.unt.edu.; .