Ala. Code § 41-10-365
For the purpose of providing funds to enable the authority to pay at their respective maturities the principal of and interest on any bonds issued by it under the provisions of this article and to accomplish the objects of this article, there are hereby irrevocably pledged to such purpose and there are hereby appropriated so much as may be necessary for such purpose of (a) the receipts from the tax levied by Sections 40-25-2 and 40-25-41 and required to be distributed to the authority in accordance with the provisions of Section 40-25-23 and, (b) to the extent that the receipts from said tax shall be insufficient for such purpose, the receipts from the tax levied by Acts 1988, 1st Ex. Sess., No. 88-869, that are required to be distributed to the authority pursuant to the provisions of Acts 1988, 1st Ex. Sess., No. 88-869. All moneys hereby appropriated and pledged shall constitute a sinking fund for the purpose of paying the principal of (premium, if any) and the interest on the bonds herein authorized.
Ala. Code § 41-10-365 (1975)