1. P. Ponsoy, ‘L’Islam et le Graal’, Denoël, Paris, 1958
2. L. Thorndike, ‘History of Magic and Experimental Science’, Vol. 2, Columbia University Press, New York, 1923, Chap. 68
3. M.A. Atwood, ‘A Suggestive Inquiry into the Hermetic Mystery’, 3rd Ed., W. Tait, Belfast, 1970, p. 72
4. S. Mahdihassan (Scientia, 1960,95, (2), 48–53; 1961,96, (6), 187–195) claims that this so-called Serpent of Ouroboros was the probable origin of August Kekulé’s dream of the benzene ring in 1865.
5. ‘A Treatise of the Names of the Philosophers Stone’, collected by William Gratacolle, transl. into English by the Paines and Care of H.P.’, London, 1652 contains a list of more than 170 synonyms.