R.G. LeTourneau, Inc. NOW, Volume 2, Number 17, September 17, 1937, periodical, September 17, 1937; (https://texashistory.unt.edu/ark:/67531/metapth1532432/m1/1/: accessed July 16, 2024), University of North Texas Libraries, The Portal to Texas History, texashistory.unt.edu.; .