1. O. Kubashewski C. B. Alcock Metallurgical Thermochemistry 1979 N. Y. 267/323
2. Phase Equilibrium Diagram Data Base, ver.2 for Windows 95”, Figure 631 published by American Ceramic Society Westerville, Ohio, 43086-6136, U. S. A.
3. Phase Equilibrium Diagram Data Base, version 2.1 for Windows 95, Figure 2647 published by American Ceramic Society Westerville, Ohio, 43086-6136, U.S.A.