@article{MAT_1966_10_2_a2,
     author = {G. Biriuk and E. A. Coddington},
     title = {Normal extensions of unbounded formally normal operators},
     journal = {Matematika},
     pages = {117--135},
     publisher = {mathdoc},
     volume = {10},
     number = {2},
     year = {1966},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MAT_1966_10_2_a2/}
}