| http://www.w3.org/ns/prov#value | - For example the compounds of the formulae: ##STR47## where R1, R3 and R4 are each alkyl or aryl groups which can be substituted, R2 and R5 are each selected from hydrogen or an alkyl group which can be substituted, A and A1 each represent a divalent organic linkage, n is an integer of at least 2 and Z is a core radical of valency n+1, are new and useful compounds.
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