| http://www.w3.org/ns/prov#value | - A preferred source of the nitrogen-containing group are polyamines, especially alkylene amines conforming for the most part to the formula ##STR1## wherein n is an integer preferably less than about 10, A is a substantially hydrocarbon or hydrogen radical, and the alkylene radical is preferably a lower alkylene radical having less than about 8 carbon atoms.
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