Muller, Helen. Letter from Helen Muller to Dr. Cyrus N. Ray - July 19, 1965], letter, July 19, 1965; (https://texashistory.unt.edu/ark:/67531/metapth1399013/m1/1/: accessed June 4, 2024), University of North Texas Libraries, The Portal to Texas History, texashistory.unt.edu; .