Texas. Legislature. House of Representatives. 80th Texas Legislature, Regular Session, House Bill 3980, Chapter 1370, legislative document, June 15, 2007; (https://texashistory.unt.edu/ark:/67531/metapth155328/m1/1/: accessed September 23, 2018), University of North Texas Libraries, The Portal to Texas History, texashistory.unt.edu; .