Diggs, Melvin M. [Letter from Melvin M. Diggs to Charles Batchelor, January 20, 1967 #4], letter, January 20, 1967; (https://texashistory.unt.edu/ark:/67531/metapth338041/m1/1/: accessed July 18, 2024), University of North Texas Libraries, The Portal to Texas History, texashistory.unt.edu; .