Watersoluble terpolymers based on three monomer units all of formula: ##STR1## (or possibly the 5-membered ring analogue) wherein the N-substituents are respectively (A) low-low e.g. dimethyl (B) low-medium e.g. methyloctyl and (C) low-higher e.g. methyllauryl or methylcetyl, in molecular size; B:C being...http://www.google.co.uk/patents/US4304894?utm_source=gb-gplus-sharePatent US4304894 - Quaternary ammonium terpolymers
