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2. Y. Izumi and M. Otake, Kagaku Sosetu 34 (1982) 116, and references therein.
3. M. Misono, K. Sakata, Y. Yoneda and W.Y. Lee, in:7th Int. Congr. on Catalysis, Tokyo 1980 (Kodansha/Elsevier, Tokyo/Amsterdam, 1981) p. 1047;
4. M. Misono, Catal. Rev. Sci. Eng. 29 (1987) 269.
5. M.T. Pope,Heteropoly and Isopoly Oxometalates (Springer, Berlin, 1983), and references therein.