@article{DAN_1986_291_5_a5,
     author = {G. A. Isaev and T. Yu. Kuliev},
     title = {Analytic properties of the boundary of the numerical range of},
     journal = {Doklady Akademii Nauk},
     pages = {1050--1053},
     publisher = {mathdoc},
     volume = {291},
     number = {5},
     year = {1986},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1986_291_5_a5/}
}