| http://www.w3.org/ns/prov#value | - M(OR)n where M is an element forming a refractory oxide, R is a lower alkyl, cycloalkyl, aryl, or aralkyl radical containing from 1 to about 8 carbon atoms, and n is the valence of M. M is preferably a transition metal of Group IIIB, IV-B or V-B and most preferably of Group IV-B, e.g., titanium or zirconium.
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