Terms with respect to which the confirmatory memoranda of the parties agree, or that are otherwise set out in a writing intended by the parties as a final expression of their agreement with respect to the terms included in the writing, may not be contradicted by evidence of a prior agreement or of a contemporaneous oral agreement, but may be explained or supplemented (1) by course of performance, course of dealing, or usage of trade (AS 45.01.303); and (2) by evidence of consistent additional terms unless the court finds the writing was intended also as a complete and exclusive statement of the terms of the agreement.
Alaska Legal Code