Osthoff, R. [Letter from R. Osthoff to H. Studtmann, February 23, 1928], letter, February 23, 1928; (https://texashistory.unt.edu/ark:/67531/metapth606274/m1/1/: accessed July 16, 2024), University of North Texas Libraries, The Portal to Texas History, texashistory.unt.edu; .