Abstract: A system of preserving the integrity of research and comparable data regularly entered into an electronically accessible memory by printing it out periodically upon a form of protected document stock which reveals the fact of copying in every xerographic copy of an original sheet of such stock, and which is accounted for, sheet by sheet, through the use of a unique serial number assigned by the manufacturer of the stock and recorded by him as issued to a given customer/user, and by the use of a record of distribution maintained by the records custodian of a given customer/user to identify specific serially-numbered sheets of such stock as having been issued to a particular person on a particular date, and who collects or receives the printed out stock as a permanent record of the information recorded.

Abstract: The text discloses for use in printing valuable documents an allover pattern of warning indicia which is merged by human sensory perception with its background but is distinguished and reproduced by xerographic copying as a result of the employment of two different screen values for the indicia and the background which are respectively within and beyond the reproductive capability of the copier machine when used in the stated context. Adjunctively, document validating indicia are also printable on such documents in a screen value beyond the reproductive capability of xerographic copiers at the lighter settings at which the lesser screen value used for said warning indicia or background will reproduce.