The Clavis Patrum Graecorum is a series of volumes published by Brepols of Turnhout in Belgium. The series aims to contain a list of all the Fathers of the Church who wrote in Greek from the 1st to the 8th centuries. For each it lists all their works, whether genuine or not, extant or not. Each work is assigned a number, which is widely used as a reference in scholarly literature. The text is in Latin. Source: Wikipedia (en)