%0 Journal Article %A János Bognár %T Non-negativity properties of operators in spaces with indefinite metric %J Annales Fennici Mathematici %D 1964 %V 336-344 %I mathdoc %U http://geodesic.mathdoc.fr/articles/10.5186/aasfm.1964.336-10/ %R 10.5186/aasfm.1964.336-10 %G en %F AFM_1964_336-344_a14