 Because of the likelihood of errors being introduced each time a manuscript was copied, the filiation of different versions of the same text is a fundamental part of the study and criticism of all texts that have been transmitted in manuscript.In Southeast Asia, in the first millennium, documents of sufficiently great importance were inscribed on soft metallic sheets such as copperplate, softened by refiner's fire and inscribed with a metal stylus.In the Philippines, for example, as early as 900AD, specimen documents were not inscribed by stylus, but were punched much like the style of today's dot-matrix printers.