@article{TM_1991_200_a23,
     author = {V. V. Napalkov and I. A. Rudakov},
     title = {Differential operators in nonconvex domains},
     journal = {Trudy Matematicheskogo Instituta imeni V.A. Steklova},
     pages = {255--260},
     publisher = {mathdoc},
     volume = {200},
     year = {1991},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/TM_1991_200_a23/}
}