In a couple of places, Jaroslav Pelikan quotes Benjamin Breckenridge Warfield's Augustine and Calvin (a book and an author I've never heard of elsewhere) as saying "the Reformation, inwardly considered, was just the ultimate triumph of Augustine's doctrine of grace over Augustine's doctrine of the church." A selection of Luther's writings shows numerous entries for Augustine in the index--not all for support, it is true.

A dip into Calvin's Institutes of Religion turns up references to Ambrose, Augustine, Jerome, Gregory Nazianzus, Basil, Chrysostom, and Bernard of Clairvaux.

[edit: the sentence on Calvin]