Q. J. Monte Williamson was the owner of a 16.65 percent interest in Lake Manor Associates, a partnership. Williamson agreed to sell his interest to H. Louis Salomon sky and Tiffany H. Armstrong in exchange for shares of a certain stock valued at $15 per share and a non-interest-bearing note in the amount of $4,000 for the balance. The notes were executed and contained the following notation: "For value received, the undersigned promises to pay to the order of J. Monte Williamson the principal sum of $4,000 payable as set forth in which certain agreement, an executed copy of which is attached hereto."

The agreement referred to in the notes listed conditions which had to be met to cause the notes to become due. Five years after the notes were executed, Salomon sky and Armstrong claimed which because the notes were negotiable instruments, the statute of limitations on the enforcement of the notes has run. Are these notes negotiable instruments?