%0 Journal Article %A A. V. Bitsadze %T On the theory of systems of partial differential equations %J Trudy Matematicheskogo Instituta imeni V.A. Steklova %D 1976 %P 67-77 %V 142 %I mathdoc %U http://geodesic.mathdoc.fr/item/TM_1976_142_a3/ %G ru %F TM_1976_142_a3