@article{TMF_1990_82_3_a10,
     author = {I. A. Vakarchuk},
     title = {Density matrices of~superfluid {helium-4.~II}},
     journal = {Teoreti\v{c}eska\^a i matemati\v{c}eska\^a fizika},
     pages = {438--449},
     publisher = {mathdoc},
     volume = {82},
     number = {3},
     year = {1990},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/TMF_1990_82_3_a10/}
}