@article{IVM_1990_9_a4,
     author = {G. A. Mikhalin and E. V. Mokhort and L. S. Teslenko},
     title = {A~core (in the sense of {Knopp)} of a~sequence and its conservative matrix means},
     journal = {Izvesti\^a vys\v{s}ih u\v{c}ebnyh zavedenij. Matematika},
     pages = {41--45},
     year = {1990},
     number = {9},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/IVM_1990_9_a4/}
}