There is hereby irrevocably pledged and appropriated such amounts of tobacco revenues retained in the special fund, and earnings thereon, as shall be necessary to pay and to redeem prior to their respective maturities the principal, interest, and premium, if any, on the authority's bonds and to pay the principal of and the interest on any refunding bonds issued to refund such bonds.
Ala. Code § 41-10-630 (1975)