Texas. Legislature. House of Representatives. 80th Texas Legislature, Regular Session, House Bill 1972, Chapter 310, legislative document, 2007-04/2007-06; (https://texashistory.unt.edu/ark:/67531/metapth154901/m1/2/: accessed December 19, 2018), University of North Texas Libraries, The Portal to Texas History, texashistory.unt.edu; .