@article{UMJ_2017_3_2_a1,
     author = {Roman R. Akopyan},
     title = {Approximation of the differentiation operator on the class of functions analytic in an annulus},
     journal = {Ural mathematical journal},
     pages = {6--13},
     publisher = {mathdoc},
     volume = {3},
     number = {2},
     year = {2017},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/UMJ_2017_3_2_a1/}
}