- HTML (Multi-page, indexed) at Christian Classics Ethereal Library (Translated by Cardinal Newman; corr. by Henry Wace)
- Spanish HTML (Multi-page, not indexed) at Diccionario Teológico Mercabá (Translator unknown)
Available at Amazon.com:
- Paperback edition, also includes the Letter to Marcellinus (Paulist Press, 1980, 166 pg).
All links verified on or after September 5, 2019