@article{DAN_1976_228_3_a7,
     author = {E. I. Pustyl'nik},
     title = {Absolutely concave functions of positive operators},
     journal = {Doklady Akademii Nauk},
     pages = {547--550},
     publisher = {mathdoc},
     volume = {228},
     number = {3},
     year = {1976},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1976_228_3_a7/}
}