@article{DE_1985_21_8_a16,
     author = {V. S. Serov},
     title = {The {Friedrichs} extension of a differential operator with a singularity},
     journal = {Differencialʹnye uravneni\^a},
     pages = {1422--1429},
     year = {1985},
     volume = {21},
     number = {8},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1985_21_8_a16/}
}