Acts 1965, 59th Leg., vol. 2, p. 317, ch. 722. Amended by Acts 1975, 64th Leg., p. 617, ch. 253, Sec. 1, eff. Sept. 1, 1975.

Amended by Acts 1981, 67th Leg., p. 2244, ch. 537, Sec. 1, eff. June 12, 1981.