Acts 1965, 59th Leg., vol. 2, p. 317, ch. 722. Amended by Acts 1973, 63rd Leg., p. 978, ch. 399, Sec. 2(C), eff. Jan. 1, 1974; Acts 1977, 65th Leg., p. 692, ch. 262, Sec. 1, eff. May 25, 1977.
Amended by Acts 1981, 67th Leg., p. 2636, ch. 707, Sec. 4(17), eff. Aug. 31, 1981; Acts 1983, 68th Leg., p. 5317, ch. 977, Sec. 7, eff. Sept. 1, 1983.