Sec. 21.105.  INTEREST AND SINKING FUND.  The Texas park development bonds interest and sinking fund, referred to as the "interest and sinking fund," is created to be used exclusively for:
(1)  paying the principal of Texas Park Development Bonds as they mature;
(2)  paying the interest on the bonds as it comes due;  and
(3)  paying exchange and collection charges in connection with the bonds.
Acts 1975, 64th Leg., p. 1405, ch. 545, Sec. 1, eff. Sept. 1, 1975.