@article{TM_1976_142_a3,
     author = {A. V. Bitsadze},
     title = {On the theory of systems of partial differential equations},
     journal = {Trudy Matematicheskogo Instituta imeni V.A. Steklova},
     pages = {67--77},
     publisher = {mathdoc},
     volume = {142},
     year = {1976},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/TM_1976_142_a3/}
}