@article{ELA_2011__22__a52,
     author = {Nakazato, Hiroshi and Bebiano, Natalia and Da Providencia, Joao},
     title = {The numerical range of linear operators on the 2-dimensional {Kre\u{i}n} space},
     journal = {The electronic journal of linear algebra},
     pages = {430--442},
     publisher = {mathdoc},
     volume = {22},
     year = {2011},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/ELA_2011__22__a52/}
}