Okla. Stat. tit. 12A, § 12A-2-202: Final written expression: parol or extrinsic evidence

Final Expression: Parol or Extrinsic Evidence.

Terms with respect to which the confirmatory memoranda of the

parties agree or which are otherwise set forth in a record intended

by the parties as a final expression of their agreement with respect

to such terms as are included therein may not be contradicted by

evidence of any prior agreement or of a contemporaneous oral

agreement but may be explained or supplemented:

(a) by course of performance, course of dealing or usage of

trade (Section 16 of this act); and

(b) by evidence of consistent additional terms unless the court

finds the record to have been intended also as a complete and

exclusive statement of the terms of the agreement.