Added by Acts 1989, 71st Leg., ch. 399, Sec. 2, eff. June 14, 1989. Amended by Acts 1991, 72nd Leg., ch. 775, Sec. 18, eff. Sept. 1, 1991; Acts 1999, 76th Leg., ch. 62, Sec. 3.03, eff. Sept. 1, 1999; Acts 1999, 76th Leg., ch. 1545, Sec. 62, eff. Sept. 1, 1999.