Okla. Stat. tit. 62, § 62-438: Bonds for city hall - Rentals paid into sinking fund

That all cities in the State of Oklahoma operating under a

charter form of government, wherein such cities may hereafter issue

bonds for the purpose of raising funds to construct a city hall

building, be and are hereby required to pay into the sinking fund

for the payment of interest and the retirement of such bonds so

issued, all rentals so derived from the use of such parts of the

city hall building as are not required for the use of the city, and

such rentals so acquired over and above maintenance shall be

irrevocably pledged for the payment of the interest and the

retirement of such bonds and shall not be used for any other

purpose.