Oklahoma constitution
Article X: revenue and taxation
Section 29

No bond or evidence of indebtedness of this State shall be valid unless the same shall have endorsed thereon a certificate, signed by the Auditor and Attorney General of the State, showing that the bond or evidence of debt is issued pursuant to law and is within the debt limit. No bond or evidence of debt of any county, or bond of any township or any other political subdivision of any county, shall be valid unless the same have endorsed thereon a certificate signed by the County Clerk, or other officer authorized by law to sign such certificate, and the County Attorney of the county, stating that said bond, or evidence of debt, is issued pursuant to law, and that said issue is within the debt limit.