Hellinghausen, F. A. [Report to W. P. Gannaway by F. A. Hellinghausen, January 28, 1964 #2], report, January 28, 1964; (https://texashistory.unt.edu/ark:/67531/metapth338420/m1/1/: accessed July 17, 2024), University of North Texas Libraries, The Portal to Texas History, texashistory.unt.edu; .