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2. FRG Patent No. 1185163 (1966).
3. N. F. Fedorov, G. K. Ivakhnyuk, D. N. Gavrilov, V. V. Tetenov, G. N. Smetanin, V. V. Samonin, O. É. Babkin, and Yu. A. Zaitsev, in Carbon-Based Adsorbents and Their Industrial Applications [in Russian], edited by T. G. Plachenov (Nauka, Moscow, 1983), p. 20.
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5. S. K. Gordeev, A. V. Vartanova, S. G. Zhukov, I. N. Gran’, V. V. Sokolov, T. I. Mazaeva, and R. G. Avarbé, RF Patent No. 2026735 (1995).