@article{RM_1972_27_6_a15,
     author = {A. B. Mitel'man},
     title = {The absence of weak lacunae between ovals of the characteristic surface of a~hyperbolic operator},
     journal = {Trudy Matematicheskogo Instituta imeni V.A. Steklova},
     publisher = {mathdoc},
     volume = {27},
     number = {6},
     year = {1972},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/RM_1972_27_6_a15/}
}