Those readers who wish to learn more about the nature of the Awful Secret, are recommended to read the following paperbacks:
Andrews, R., and O. Schellenberger, The Tomb of God, (Warner, London, 1996; ISBN 0 7515 1961 8)
Baigent, M., R. Leigh and H. Lincoln, The Holy Blood & the Holy Grail, (Arrow, London, 1996; ISBN 0 09 968241 9)
Gardner, L., Bloodline of the Holy Grail, (Element, Shaftesbury, 1996; ISBN 1 86204 152 0)
Theiring, Barbara, Jesus the Man, (Corgi, London, 1993; ISBN 0 552 13950 5)
Also many Internet sites reached through Rennes-le-Chateau etc.