^E.R.Caley, The Leyden Paprus X: An English Translation with Brief Notes, p.1149: "These two papyri have, however, upon the basis of unquestioned philological and paleographic evidence, been ascertained to have been written at about the end of the third century A.D. so that they are by far the earliest original historical evidence that we have in our possession concerning the nature and the extent of ancient chemical knowledge."
^Massie, Keyser, Greek science of the Hellenistic era: a sourcebook, p.251