1. M. Berthelot, ‘Archéologie et Histoire des Sciences’, Steinheil, Paris, 1906
2. J. Altman, Gold Bull., 1979, 12, (2), 75–82
3. C. Plinius Secundus, ‘Naturalis Historia’, XXXIII, 18, 19
4. W. S. Prideaux Clark, ‘Memorials of the Goldsmiths’ Company’, London, 1896
5. Theophilus, ‘De Diversis Artibus’, Book I, Chapter 23, translated into English by J. G. Hawthorne and C. S. Smith, ‘On Divers Arts: The Treatise of Theophilus’, The Chicago University Press, Chicago, 1963, pp. 39–41