Texas. Legislature. General and Special Laws of The State of Texas Passed By The Regular Session of the Sixty-Seventh Legislature, Volume 2, legislative document, 1981; (https://texashistory.unt.edu/ark:/67531/metapth221801/m1/3/: accessed May 19, 2019), University of North Texas Libraries, The Portal to Texas History, texashistory.unt.edu; .