1. August Strindberg Papers, Carton No. 30, preserved in Handskriftavdelningen Kungliga Biblioteket (The Royal Library), Stockholm
2. G.B. Kauffman,Gold Bull., 1983,16, (1), 21–28
3. M.E. Weeks, ‘Discovery of the Elements’, 7th Ed., completely revised and new material added by H.M. Leicester, Journal of Chemical Education, Easton, Pennsylvania, 1968, pp. 6–13
4. G. Allen, ‘Gold!’, Thomas Y. Crowell & Co., New York, 1964, Chap. 1
5. J. Needham with L. Gwei-Djen, ‘Science and Civilisation in China’, Vol. 5, Part 2, Cambridge University Press, New York, 1974