prov:value
| - wherein each of R1, R2, R3, and R4 is independently a hydrogen or an organic group having, inclusively, in totality up to 18 carbon atoms, wherein at least one of R1, R2, R3, and R4 is an organic group, wherein the organic group is independently a hydrocarbon group having up to 8 carbon atoms, and is an alkyl, alkylidene, heterocyclic alkyl, cycloalkyl, aryl, alkenyl, or cycloalkenyl group or a hy
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