Conn. Gen. Stat. § 42a-2A-202: Parol or extrinsic evidence.

(a) Terms on which the confirmatory records 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 the included terms, may not be contradicted by evidence of any previous agreement or of a contemporaneous oral agreement. However, terms in such a record may be supplemented by evidence of:

(1) Consistent additional terms, unless the court finds that the record was intended as a complete and exclusive statement of the terms of the agreement; and

(2) Course of performance, course of dealing or usage of trade.

(b) Terms in a record may be explained by evidence of course of performance, course of dealing or usage of trade without a preliminary determination by the court that the language used is ambiguous. Terms in a record may also be explained from other sources as determined by the court under applicable law.