Tex. Gov't Code § 813.501
Service creditable in the employee class of membership is:
Acts 1981, 67th Leg., p. 1876, ch. 453, Sec. 1, eff. Sept. 1, 1981. Renumbered from Vernon's Ann.Civ.St. Title 110B, Sec. 23.501 and amended by Acts 1989, 71st Leg., ch. 179, Sec. 1, eff. Sept. 1, 1989.