@article{MZM_1997_61_6_a16,
     author = {A. A. Lokshin},
     title = {On the concavity of the surface of eigenvalues},
     journal = {Matemati\v{c}eskie zametki},
     pages = {946--949},
     publisher = {mathdoc},
     volume = {61},
     number = {6},
     year = {1997},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MZM_1997_61_6_a16/}
}