The bonds shall state in substance that:
(a) The bond and interest are payable solely from:
(1) The gross or net, as the case may be, revenues from the operation of the parking place or places acquired and improved with the proceeds, if such is the case.
(2) The net revenues, or a portion thereof, from parking meters on certain public ways within the district, if such is the case.
(3) To the extent provided in this part, from a limited (stating the limits) ad valorem assessment to be levied upon taxable real property in the district, if such be the case.
(b) Neither the city nor any of its officers is to be held otherwise liable for its principal or interest.