Apocalypse Of Peter
Note that you only need to read the Introduction and the two sections titled "The Akhmim Fragment" and "Appendix: Second Book of the Sibylline Oracles". You do not need to read the section titled "The Ethiopic Text" unless you wish to.
Early Christian Doctrine
Augustine: City of God
Electronic Reserve @ WU: Early Christian Doctrine > Augustine: City of God
Origen: On First Principles
Electronic Reserve @ WU: Early Christian Doctrine > Origen: On First Principles