1. M. J. Cabell, Analyst77, 866 (1952).
2. E. P?ibil undP. Schneider, Coll. trav. chim. TchécoslovaquieA 5, 886 (1950).
3. J. S. Fritz undJ. J. Ford, Pittsburg Conf., March 1953, Analyt. Chemistry25, 521 (1953).
4. K. ter Haar, Diskussion des Vortrages vonM. J. Cabell, Oxford 1952, Analyst77, 866 (1952).
5. K. ter Haar undJ. Bazen, Analyt. Chim. Acta9, 235 (1953).