1. W.C. Moffatt, H.K. Bowen: J. Mat. Sci., 24 (1989), pp.3984-3990.
2. N. Kapuri, K.N. Rai, G.S. Upadhyaya: Interceram, 45 (1996), pp.427-430.
3. K. Nieszery, K.L. Weisskopf, G. Petzow, W. Pannhorst: High Tech Ceramics, Materials Science Monographs, 38A, Ed. P. Vincenzini, Elsevier Science Publishers B.V., Amsterdam, The Netherlands, 1987, pp.841-849.
4. N.A. Travitzky, N. Claussen: J. Eur. Ceram. Soc., 5 (1989), pp.327-331.
5. H.M. Jang: J. Am. Ceram. Soc., 78 (1995) pp.723-727.