1. 9) A. RAMAN: Z. Metallk., 67 (1976) 11, p.780
2. 10) A. RAMAN: Z. Metallk., 68 (1977) 3 , p.163
3. 11) W. HESSENBRUCH: Metalle and Legierungen fur hohe Tempeaturen, 1 Aufl., (1940), p.105 [Julius Springer]
4. 13) O. KUBASCHEWSKI, E. LL. EVANS and C.B. ALCOCK: Metallurgical Thermochemistry, 4th ed., (1967), p.421 [Pergamon Press]
5. 14) C.E. HOLLEY, JR., E.J. HUBER, JR., and F.B. BAKER: Progress in the Science and Technology of the Rare Earths, Vol. 3, L. EYRING, (1968), p.343 [Pergamon Press]