If the signed memorandum refers to another written instrument, extrinsic evidence is admissible to identify such other instrument.1 If written contract provides for the division of "land purchased of" the other party without further description, and a deed for the land is subsequently given without reference to the written contract, oral evidence is admissible to show that no other land was contracted for than that conveyed.2 The reference to the other writing must, however, either be made expressly, or must appear from the terms of the two instruments when compared.3