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2. E. M. LEVIN, C. R. ROBBINS, and H. F. McMURDIE: ‘Phase diagrams for ceramists’, 1 edn, (ed. M. K. Reser), 123; 1964, Columbus, OH, The American Ceramic Society.
3. P. BRACKE, H. SCHURMANS, and J. VERHOEST: ‘Inorganic fibres and composite materials’, l edn, Chap 2-7, 11-75, 1984, Oxford, Pergamon.