prov:value
| - thylene, octamethylene, decamethylene or 3-thiapentamethylene group) or a phenylene group(o-phenylene, m-phenylene or p-phenylene)] or a metal salt (the metal being, for example, barium, nickel, manganese, calcium, zinc, iron, sodium, cobalt or tin) or lower alkyl ester (preferably having from 1 to 4 carbon atoms in the alkyl group, e.g. amethyl, ethyl, propyl, isopropyl or butyl ester) thereof; a
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