| http://www.w3.org/ns/prov#value | - When R1 to R4 in the above-mentioned formula (Ia) represent a substituted hydrocarbon oxy group, it is preferably an alkoxy group having 1 to 30 carbon atoms (more preferably having 1 to 10 carbon atoms, further preferably having 1 to 9 carbon atoms), a cycloalkoxy group having 3 to 30 carbon atoms (more preferably having 3 to 20 carbon atoms, particularly preferably having 3 to 9 carbon atoms), a
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