| Code | Title. | Author. | Date | Lang |
|---|---|---|---|---|
| [O] | What the Bible Teaches, A thorough and comprehensive study of all the Bible has to say concerning the great doctrines of which it treats. | R. A. Torrey. | 1898 | ENG |
| [O01] | An Introduction to the Study of Christian Apologetics. | Arthur R. Gray. | 1912 | ENG |
| [O02] | A Handbook of Christian Apologetics. | Alfred Earnest Garvie. | 1920 | ENG |
| [O03] | Principles of Christian Apologetics. | T. J. Walshe. | 1919 | ENG |
| [O04] | Apologetics, or Christianity Defensively Stated. | Alexander Balmain Bruce. | 1924 | ENG |
| [O11] | Historical Evidence of the New Testament. | S. L. Bowman. | 1903 | ENG |
| [O12] | A System of Christian Evidence. | Leander S. Keyser. | 1922 | ENG |
| [O51] | Catholic Doctrine. | Richard Challoner. | ENG |