@article{IVM_1986_12_a7,
     author = {V. V. Kovtunets},
     title = {Differential properties of an operator of best approximation with interpolation},
     journal = {Izvesti\^a vys\v{s}ih u\v{c}ebnyh zavedenij. Matematika},
     pages = {36--42},
     year = {1986},
     number = {12},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/IVM_1986_12_a7/}
}