1. M. Okihama, J. Kunitake, Jpn. Kokai Tokkyo Koho., JP 08,198,790 (1996).
2. M. Okihama, J. Kunitake, Jpn. Kokai Tokkyo Koho., JP 08,268,943 (1996).
3. M. Okihama, J. Kunitake, Jpn. Kokai Tokkyo Koho., JP 09,067,287 (1996).
4. Heteropoly compounds of molybdenum and tungsten
5. Fine Chemicals through Heterogeneous Catalysis,2001