CantrellB. K.ZellerH. W.WilliamsK. L., US Bureau of Mines Report 1C 9141, 18 (1987).
5.
CornilsenB. C.JohnsonJ. H.LoyselleP. L.CarlsonD. H., in Proceedings of the VIIth International Pneumoconioses Conference, Part 1, No. 90-108, GlennR.E., Ed. (U.S. Department of Health and Human Services Pittsburgh, Pennsylvania, 1990), p. 656.
6.
CornilsenB. H.ShanX.JohnsonJ. H.CarlsonD. H., in Proceedings of the Third International Symposium on Respiratory Dust in the Mineral Industry, FrantzR. L.RamaniR. V., Eds. (The Pennsylvania State University, University Park, Pennsylvania, 1991), Chap. 10, p. 93.
7.
ClarksonR. B.WangW.BrownD. R.CrookhamH. C.BelfordR. L., in Magnetic Resonance of Carbonaceous Solids, (American Chemical Society, Washington, D.C., 1993), p. 507.