| http://www.w3.org/ns/prov#value | - Of the above compounds represented by Formula (I), particularly preferred are the compounds in which R1 and R2 each are a hydrogen atom, carboalkoxymethyl, chloromethyl, chloroethyl, cyanomethyl, or cyanoethyl, and at least one of R1 and R2 is a group other than a hydrogen atom, or R1 and R2 form the following group: ##STR7## and R3 and R4 each is a hydrogen atom, a halogen atom, or an alkyl group
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