The present pertains to an improved method of internally sizing a cellulosic article and an improved internally sized cellulosic article where a water-dispersible, water- and alkali-insoluble internal sizing agent from an interpolymer of an ethylenically unsaturated hydrocarbon monomer and an ethylenically unsaturated carboxylic acid comonomer is applied to fiber stock or pulp slurry some amount of time subsequent to the instance of application of a retention aid. The invention also includes a novel internal sizing composition where the interpolymer is rendered water-dispersible by reaction with an inorganic neutralizing cationic compound. The improved method is particularly well suited for paper making wherein substantially improved sizing performance is obtainable. Internal sizing agents based on inorganic neutralizing cationic compounds such as, for example, potassium hydroxide, provide the surprising advantage of hard water resistance.