1. Burden, H.: Modern use of hard metal. Alloy Metals Rev.5, 47 (1948).
2. Drinker, Ph., andTh. Hatch: Industrial dust. New York: McGraw-Hill Co. 1936.
3. Fairhall, L. T., R. G. Keenan, Brinton andP. Hugh: U.S. Publ. Health Rep.64, 485 (1949).
4. Fairhall, L. R., H. T. Castberg, J. Carozzo andH. P. Brinton: Ocoup. Med.4, 317 (1947).
5. Forssman, S.: Persönliche Mitteilung, 1947. Publiziert in Third Int. Conference of Experts on Pneumoconiosis of Procedings, Bd. 1, S. 12, 120. Geneva 1953.