@article{MZM_1976_19_5_a10,
     author = {N. A. Shananin},
     title = {An example of a~locally unsolvable differential equation of quasiprincipal type with a~real-valued weighted principal symbol},
     journal = {Matemati\v{c}eskie zametki},
     pages = {755--761},
     year = {1976},
     volume = {19},
     number = {5},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MZM_1976_19_5_a10/}
}