For fuller discussion and citation of scholarly publications, see L.W. Hurtado, The Earliest Christian Artifacts: Manuscripts and Christian Origins (Grand Rapids: Eerdmans, 2006), pp. 135–154; Larry W. Hurtado, “The Staurogram in Early Christian Manuscripts: The Earliest Visual Reference to the Crucified Jesus?” in T.J. Kraus and T. Nicklas, eds., New Testament Manuscripts: Their Texts and Their World (Leiden/Boston: Brill, 2006), pp. 207–226. The most important previous studies were by K. Aland, “Bemerkungen zum Alter und Entstehung des Christogramms anhand von Beobachtungen bei P66 und P75,” in Studien zur Überlieferung des Neuen Testaments und seines Textes (Berlin: De Gruyter, 1967), pp. 173–179; and Matthew Black, “The Chi-Rho Sign: Christogram and/or Staurogram?” in W.W. Gasque and R.P. Martin, eds., Apostolic History and the Gospel: Essays Presented to F.F. Bruce (Grand Rapids: Eerdmans, 1970), pp. 319–327.