Such revenue bonds shall not be general obligations of the municipality or county, and in no event shall the revenue bonds constitute an indebtedness of the municipality or county within the meaning of any constitutional or statutory limitation. It shall be plainly stated on the face of each bond that the same has been issued under the provisions of this act, and under the terms of 60 O.S.1951, §§ 176-180, inclusive, as amended by Sections 1 and 2, Chapter 4, Title 60, page 277, Oklahoma Session Laws 1953 (60 O.S.Supp.1959, §§ 176 and 177), relating to public trusts, and that it does not constitute an indebtedness of the municipality or county within any constitutional or statutory limitation. The principal of and the interest on the revenue bonds, and paying agent's fees, shall be payable in the first instance from gross revenues derived from the lands, buildings, and/or facilities acquired, constructed, reconstructed, extended, and/or improved, in whole or in part, with the proceeds of the bonds. In addition, the trustees, with prior approval of the municipality or county, are authorized to pledge to and use for the payment of the principal of and interest on the bonds, and paying agent's fees, such revenues derived from other lands, buildings, and/or facilities used and useful for securing and developing industry and/or surplus revenues derived from water, sewer, gas, and electric utilities owned by the municipality or county and by such beneficiary transferred or leased to the trustees for such purpose, provided that such transfer or lease shall have been included in the question voted upon and approved in the election required to be held under Section 4 of this act.¹ For the purpose of this section the phrase “surplus revenues” is hereby defined to be any revenues over and above the costs of financing the general government and utility functions of the municipality or county in any fiscal year, or any prior commitments of such revenues.