The Discussions - Sowle and McCartney's discussions both before and at the time of signing are evidence that they intend the written agreement to be the complete and exclusive statement of the terms of their agreement.

TThe Signing of The Agreement - The fact that they read and understood the entire agreement clause, and then signed the agreement is evidence that they intend the written agreement to be the complete and exclusive statement of the terms of their agreement./a>

Both of the discussions and the signing of the agreement.