@article{SM_1972_17_2_a7,
     author = {F. A. Berezin},
     title = {Convex operator functions},
     journal = {Sbornik. Mathematics},
     pages = {269--277},
     publisher = {mathdoc},
     volume = {17},
     number = {2},
     year = {1972},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/SM_1972_17_2_a7/}
}