prov:value
| - f the formula I ##STR30## in which R1 and R2 are identical or different and are a hydrogen atom, a C1 -C10 -alkyl group, a C1 -C10 -alkoxy group, a C6 -C10 -aryl group, a C6 -C10 -aryloxy group, a C2 -C10 -alkenyl group, a C7 -C40 -arylalkyl group, a C7 -C40 -alkylaryl group, a C8 -C40 -arylalkenyl group or a halogen atom,R3 and R4 are identical or different and are a hydrogen atom, a halogen atom
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