1. Berl, F., and Bender, F.Chem. Zlg., 1930,54, 913–14.
2. Sir David BrewsterBr. Assoc. Rep., 1840,2, 5–6; 1859,2, 11; 1860,2, 9–12;Edinb. Roy. Soc. Trans., 1864,23, 193.
3. Ford, K. L.J. Amer. Cer. Soc., 1922,5, 837.
4. Guillot, M.Comp. Rend., 1934,198, 2093–2095.
5. Noel HeatonJ. Soc. Arts., 1907,55 468–484.