@article{MZM_1997_62_5_a15,
     author = {A. M. Gomilko and G. V. Radzievskii},
     title = {On the numerical ranges of a family of commuting operators},
     journal = {Matemati\v{c}eskie zametki},
     pages = {787--791},
     publisher = {mathdoc},
     volume = {62},
     number = {5},
     year = {1997},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MZM_1997_62_5_a15/}
}