1. G. C. WEI and P. F. BECHER,Amer. Ceram. Soc. Bull. 64 (1985) 298.
2. N. CLAUSSEN and G. PETZOW,J. Phys. Colloq. (1986) C1-693.
3. D. F. HASSON, S. M. HOOVER and C. R. CROWE,J. Mater. Sci. 20 (1985) 4147.
4. F. POTT,Staub-Reinhalt Luft 38 (1978) 486.
5. M. F. STANTON and M. LAYARD, In “Workshop on Asbestos: Definitions and Measurement Methods”, edited by Grabatt, Lafleur and Heinrich. (National Bureau of Standards Special Publication 506, 1978) p. 143.