1. F. Chemnitius, Chem.-Ztg.51, 611 (1927);F. Weigand, Z. angew. Chem.19, 139 (1906).
2. F. Selmi, Gazz. chim.5, 256 (1875).
3. G. Klein undE. Herndlhofer, Österr. bot. Z.76, 222 (1927).
4. F. Pavelka, Microanalisi, Bd. I, Inorganica qualitativa. Firenze: Cya. 1954.