Reference
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- Browning , E. 1961 . Toxicity of Industrial Metals , 125 – 129 . London : Butterworth's .
- Patty , F. A. , ed. 1963 . Industrial Hygiene and Toxicology , 2nd ed. , Vol. II , 1037 New York : Interscience Publishers .
- 1967 . American Conference of Governmental Industrial Hygienists, Threshold Limit Values for 1967. 7 Cincinnati I., Ohio