Jason BeDuhn, The First New Testament: Marcion’s Scriptural Canon (Polebridge, 2013).
David Brakke, “Canon Formation and Social Conflict in Fourth Century Egypt: Athanasius of Alexandria’s Thirty Ninth Festal Letter,” Harvard Theological Review 87 (1994)395–419.
J.K. Elliott, The Apocryphal New Testament: A Collection of Apocryphal Christian Literature in an English Translation Based on M.R. James (Oxford: Clarendon, 1993).
Hans Josef Klauck, Apocryphal Gospels: An Introduction (London T&T Clark, 2003).
Helmut Koester, Ancient Christian Gospels: Their History and Development (London: SCM; Philadelphia: Trinity Press International, 1990).
L. M. MacDonald and J. M. Sanders, eds., The Canon Debate (Hendrickson, 2002).
Wilhelm Schneemelcher, New Testament Apocrypha (2 vols.); Cambridge: Clarke; Louisville: Westminster/John Knox, 1991-92).
Hans von Campenhausen, Formation of the Christian Bible (Philadelphia: Fortress, 1973).
Timeline of NT Canon, at Google Images