| http://www.w3.org/ns/prov#value | - In the above-mentioned general formula [A-V], the alkyl groups represented by Rb1 and Rb2 are preferably those having 1 to 5 carbon atoms, such as a methyl, ethyl, propyl, isopropyl, or butyl group; if each of them is an alkoxy group, it is preferably one having 1 to 5 carbon atoms, such as a methoxy, ethoxy, or propoxy group; if each of them is an aryl group, it may be, for example, a phenyl, 4-h
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