prov:value
| - wherein each of R1, R2, R3, and R4 is independently a hydrogen or an organic group, and wherein at least one of R1, R2, R3, and R4 is an organic group, such as, an alkyl, alkylidene, heterocyclic alkyl, cycloalkyl, aryl, alkenyl, or cycloalkenyl group, a hydroxy-substituted derivative thereof, optionally including within its hydrocarbon chain a S, O, or N atoms, e.g., forming an ether (including a
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