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2. L.J.B. Hofer: Exp. Methods in Catal. Research, ed. by B.B. Anderson, p. 409. Academic Press, New York 1968.
3. P.W. Selwood: Magnetochemistry, p. 149. Interscience Publishers, New York 1956.
4. Li Fengyi, Liu Liangtan, Luo Leitao, Lu Weiqi, Yi Qunging: J. Less-Comm. Met.,126, 89 (1986).