Texas. Legislature. House of Representatives. 81st Texas Legislature, Regular Session, House Bill 3638, Chapter 974, legislative document, June 19, 2009; (https://texashistory.unt.edu/ark:/67531/metapth148750/m1/1/: accessed June 23, 2018), University of North Texas Libraries, The Portal to Texas History, texashistory.unt.edu; .