From the perspective of the historian, a large part of human history is known through physical objects from the past that have been found or preserved, particularly in written documents. Digital records are easy to create but also easy to delete and modify. Changes in storage formats can make recovery of data difficult or near impossible, as can the storage of information on obsolete media for which reproduction equipment is unavailable, and even identifying what such data is and whether it is of interest can be near impossible if it is no longer easily readable, or if there is a large number of such files to identify. Information passed off as authentic research or study must be scrutinized and verified.