Okla. Stat. tit. 16 § 37b
All deeds, mortgages, releases, oil and gas leases, powers of attorney and other instruments of writing for the conveyance or encumbrance of any lands, tenements or hereditaments situated within this state, now of record or hereafter recorded which are executed and acknowledged or proved in any state, territory, District of Columbia or foreign country, in conformity with the law of such state, territory, District of Columbia or foreign country, or in conformity with the Federal Statutes, shall be as valid as to execution and acknowledgment thereof, only, as if executed and acknowledged within this state in conformity with the provisions of the laws of this state. Provided this act shall not validate any deed, mortgage, releases, oil and gas leases, powers of attorney, and other instruments of writing for the conveyance of any lands, tenements, or hereditaments, the validity of which is in litigation upon the effective date of this act. Provided this act shall not validate any execution or acknowledgment fraudulently obtained.
Okla. Stat. tit. 16, § 37b