My current research projects have led me to briefly engage the topic of intertextuality. Patristic intertextuality provides a conundrum of complications. Are texts readily available? Geographically available? What other conflations have patristic authors introduced? And others. (More to follow on such questions). A few books are helpful to engaging this conversation, and upon further inquiry, will hopefully point to others. David Nienhuis, Not By Paul Alone: The Formation of the Catholic Epistle Collection and the Christian Canon, briefly engages such questions. Nienhuis gives his personal 5-fold methodology (29–32). (Brian Renshaw engages this chapter)
1. “First, in the case of uncertain allusions and echoes, I will exegete the broader contexts of the passages in question for assistance in adjudication of dependence.”
2. "Second, I will refuse to stand on any parallel that can be accounted for on the basis of earlier source material."
3. "Third, we note that church fathers often cite apostolic texts intertextually" (i.e. multiple apostolic texts are conflated into a phrase so as to nearly eliminate a single tradition).
4. "Fourth, I will take into consideration other comments the writer makes about the apostolic figure associated with the writing we are exploring."
5. "Finally, my analysis will investigate how the patristic writer in question used the proto-CE texts themselves."
Andrew Gregory. The Reception of Luke and Acts in the Period before Irenaeus. Tübingen: Mohr Siebeck, 2003.
M. Thompson. Clothed with Christ: The Example and Teaching of Jesus in Romans 12.1–15.13. Journal for the Study of the New Testament Supplement Series 59. Sheffield: JSOT Press, 1991.
D. Jeffrey Bingham. Irenaeus' Use of Matthew's Gospel in Adversus Haereses. Traditio Exegetica Graeca 7. Leuven, Belguim: Peeters, 1998.
Joseph Kelly (Blog) directed me to a greater discussion on intertextuality.