prov:value
| - R3 and R4 are identical or different and are a hydrogen atom, a halogen atom, a C1 -C10 -alkyl group, which may be halogenated, a C6 -C10 -aryl group, an --NR2 10, --SR10, --OSiR3 10, --SiR3 10 or --PR2 10 radical in which R10 is a halogen atom, a C1 -C10 -alkyl group or a C6 -C10 -aryl group,
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