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The basic notion of the parol evidence rule is that a writing intended by the parties to be a final expression of their agreement may not be contradicted by certain kinds of evidence. J. Calamari & J. Perillo, Contracts §3-2, at 135-36 (3d ed. 1987). 

Section 2--202 of the UCC recites the statute's parol evidence rule: '§2--202. Final Written 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 writing intended by the parties as a final expression of their agreement with respect to such terms as ...