@article{CMFD_2018_64_1_a9,
     author = {A. Yu. Savin},
     title = {On homotopic classification of elliptic problems with contractions and $K$-groups of corresponding $C^*$-algebras},
     journal = {Contemporary Mathematics. Fundamental Directions},
     pages = {164--179},
     publisher = {mathdoc},
     volume = {64},
     number = {1},
     year = {2018},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/CMFD_2018_64_1_a9/}
}