Die Griechischen Christlichen Schriftsteller and Corpus Scriptorum Ecclesiasticorum Latinorum Online

Significant portions of two magisterial series of critical editions for Christian texts from Late Antiquity can be easily downloaded from enumerated lists linked to archive.org and Google Books: Die Griechischen Christlichen Schriftsteller (GCS), available at Roger Pearse and Patrologia Latina, Graeca, & Orientalis (PLGO; through Scribd); and Corpus Scriptorum Ecclesiasticorum Latinorum (CSEL), also available at Roger Pearse and the PLGO.  While all of the texts from the series Sources Chrétiennes, founded in 1942, are still under copyright, useful information on the many volumes can be found on the Institute’s website.  Similarly, Brepols Corpus Christianorum, and its various subseries, are under copyright; the Series Latina is available by subscription in the Library of Latin Texts.