[Handwritten Letter from Harris Oppenheimer to Arthur M. Alpert, July 7, 1964], letter, July 7, 1964; (https://texashistory.unt.edu/ark:/67531/metapth1472658/m1/1/: accessed June 24, 2024), University of North Texas Libraries, The Portal to Texas History, texashistory.unt.edu.; .