UNDER THE PAROL EVIDENCE RULE, NO ADDITIONAL OR CONTRADICTORY TERMS TO THIS WRITTEN AGREEMENT CAN BE ADMITTED TO SHOW THAT, AT OR BEFORE THE SIGNING OF THE DOCUMENT, OTHER OR DIFFERENT TERMS WERE ORALLY AGREED UPON BY THE PARTIES.

     (Sps. Agbada v. Inter-Urban Developers, Inc., 438 Phil. 168, 192 (2002).  Thus, the terms of the Katibayan should be the prevailing terms of the transaction between the parties, not any oral or side agreement the petitioner alleged. (Dulce Pamintuan vs. People of The Philippines, G.R. No. 172820, June 23, 2010, Brion, J.).