@article{TIMM_2014_20_1_a1,
     author = {R. R. Akopyan},
     title = {Best approximation of the differentiation operator on the class of functions analytic in a~strip},
     journal = {Trudy Instituta matematiki i mehaniki},
     pages = {9--16},
     year = {2014},
     volume = {20},
     number = {1},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/TIMM_2014_20_1_a1/}
}