I'm finally getting around to something that I've always wanted to do for academic purposes, that is read the Koran. If you read the last First Things issue, there was a great article on heretical Christian documents being employed in the construction of the Koran.
I've recently learned that the Koran seems to refer to the following heretical Christian apocryphal books:
- Proto-Evangelion of James
- Infancy Gospel of Thomas
- Gospel of Pseudo-Matthew
- Arabic Infancy Gospel
- Taitian's Syriac Diatessaron (blend of the four Gospels) may also be a source