1. K. Scheringa, Chem. Weekbl.30, 92 (1933).
2. Z. Karaoglanov, Z. analyt. Chem.114, 81 (1938).
3. P. Wenger undA. R. Duckert, Helv. Chim. Acta26, 1465 (1943).
4. H. Behrens undP. Kley, Mikrochemische Analyse. Leipzig: 1915.
5. N. v. Zweigbergk, Svensk Kem. Tidskr.25, 94 (1913);C. A. Jacobson, Encyclopedia of Chemical Reactions, Bd. VI. New York: Reinold. 1956. S. 173 (VI, 780).