Hagen, William. [Letter from William Hagen to the Reverend R. Osthoff, July 30, 1929], letter, July 30, 1929; (https://texashistory.unt.edu/ark:/67531/metapth591396/m1/1/: accessed July 16, 2024), University of North Texas Libraries, The Portal to Texas History, texashistory.unt.edu.; .