| http://www.w3.org/ns/prov#value | - R3 and R4, independently of one another, denote a hydrogen atom, a halogen atom, a C1 -C4 -alkyl group, a C1 -C4 -alkoxy group, a C6 -C10 -aryl group or a C2 -C6 -alkenoxy group, preferably a hydrogen atom or methyl, in particular a hydrogen atom;
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