| http://www.w3.org/ns/prov#value | - wherein R is a tetravalent aromatic radical, preferably containing at least one ring of six carbon atoms, said ring characterized by benzenoid or aromatic unsaturation, the four carbonyl groups being attached directly to separate carbon atoms in a ring and each pair of carbonyl groups being attached to adjacent carbon atoms in a ring of the R radical; and wherein R??? is a divalent benzenoid radic
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