Ikenberry, W. P. [Letter from W. P. Ikenberry to T. N. Carswell - September 30, 1970], letter, September 30, 1970; (https://texashistory.unt.edu/ark:/67531/metapth1397935/m1/1/: accessed June 17, 2024), University of North Texas Libraries, The Portal to Texas History, texashistory.unt.edu; .