References
- Wolf , R. Jan. 1958 . Silicas , Hi-Sil Bulletin No. Vol. 16 , Jan. , Barberton , Ohio : Columbia-Southern Chemical Corporation .
- Volk , H. 1960 . The Health of Workers in a Plant Making Highly Dispersed Silica . Arch. Environ. Health , 1 Aug. : 125 – 128 .