United States. Bureau of the Census. P.L. 94-171 County Block Map (2010 Census): Grayson County, Block 25, map, December 10, 2010; (https://texashistory.unt.edu/ark:/67531/metapth384792/m1/1/: accessed October 23, 2018), University of North Texas Libraries, The Portal to Texas History, texashistory.unt.edu; .