Hurtado, Larry (2006). "The Staurogram in Early Christian Manuscripts: the earliest visual reference to the crucified Jesus?". In Kraus, Thomas (ed.). New Testament Manuscripts. Leiden: Brill. pp. 207–26. hdl:1842/1204. ISBN978-90-04-14945-8.
Hurtado (2006), citing F. J. Dölger, Sol Salutis (1920), p. 61 (note 2).
Ephraem in sanctam Parasceven, Ephraem Syri opera omnia quae extant graece — syriace — latine Tom. III Romae 1746, p. 477.