Dallas (Tex.). Police Department. [Letter to David W. Belin from J. C. Day, April 23, 1964], letter, April 23, 1964; (https://texashistory.unt.edu/ark:/67531/metapth339822/m1/1/: accessed August 25, 2019), University of North Texas Libraries, The Portal to Texas History, texashistory.unt.edu; .