Reference
- Patty , F. A. 1963 . Industrial Hygiene and Toxicology , Vol. II , 1724 – 1726 . New York : Interscience Publishers .
- American Conference of Governmental Industrial Hygienists . Documentation of Threshold Limit Values revised edition . pp. 29
- 1966 . Pennsylvania Department of Health, Article 432, Regulations Establishing Threshold Limits in Places of Employment, as amended . : 6