@article{UMJ_2017_3_2_a5,
     author = {Elena E. Berdysheva and Maria A. Filatova},
     title = {On the best approximation of the infinitesimal generator of a contraction semigroup in a {Hilbert} space},
     journal = {Ural mathematical journal},
     pages = {40--45},
     publisher = {mathdoc},
     volume = {3},
     number = {2},
     year = {2017},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/UMJ_2017_3_2_a5/}
}