July 24, 2017, 4:11 p.m.
Geological Survey (U.S.). Martinsville Quadrangle, map, 1974; Reston, Virginia. (https://texashistory.unt.edu/ark:/67531/metapth454083/: accessed April 21, 2019), University of North Texas Libraries, The Portal to Texas History, https://texashistory.unt.edu; crediting UNT Libraries Government Documents Department.