Hagen, William. [Letter from William Hagen to the Reverend R. Osthoff, June 2, 1927], letter, June 2, 1927; (https://texashistory.unt.edu/ark:/67531/metapth591357/m1/1/: accessed April 25, 2018), University of North Texas Libraries, The Portal to Texas History, texashistory.unt.edu; .