@article{DE_1975_11_11_a15,
     author = {S. M. Shugrin},
     title = {Strong and weak extension of differential operators},
     journal = {Differencialʹnye uravneni\^a},
     pages = {2067--2082},
     publisher = {mathdoc},
     volume = {11},
     number = {11},
     year = {1975},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1975_11_11_a15/}
}