| http://www.w3.org/ns/prov#value | - Further, there is disclosed in U.S. Pat. No. 3,723,333, issued Mar. 27, 1973, the use of compounds having the formula ##STR1## and a water-soluble, complex-forming compound which contains at least one phosphonate or N-dimethylenephosphoric acid group, wherein X is OH or NH2 and R is an alkyl radical of from 1 to 5 carbon atoms.
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