Okla. Stat. tit. 16 § 34
When real estate is conveyed or encumbered by an instrument in writing by a person who cannot write his or her name, the person shall execute the same by a mark, and the person's name shall be written near the mark by one of two persons who saw the mark made, who shall write their names on the instrument as witnesses. In case the instrument is acknowledged, then the officer taking the acknowledgment shall, in addition to the other necessary recitals in the acknowledgment, state that the grantor executed the instrument, by inserting in the form of acknowledgment provided in Section 33 of this title by individuals after the words "foregoing instrument" the words "by the person's mark, in my presence and in the presence of ____and ____as witnesses".
Okla. Stat. tit. 16, § 34