Some 250 known manuscripts of Plato survive. The texts of Plato as received today apparently represent the complete written philosophical work of Plato and are generally good by the standards of textual criticism. No modern edition of Plato in the original Greek represents a single source, but rather it is reconstructed from multiple sources which are compared with each other. These sources are medieval manuscripts written on vellum (mainly from 9th to 13th century AD Byzantium), papyri (mainly from late antiquity in Egypt), and from the independent "testimonia" of other authors who quote various segments of the works (which come from a variety of sources). The text as presented is usually not much different from what appears in the Byzantine manuscripts, and papyri and testimonia just confirm the manuscript tradition. In some editions however the readings in the papyri or testimonia are favoured in some places by the editing critic of the text. Reviewing editions of papyri for the "Republic" in 1987, Slings suggests that the use of papyri is hampered due to some poor editing practices.