@article{ELA_1996__1__a5,
     author = {Li, Chi-Kwong and Tsing, Nam-Kui and Uhlig, Frank},
     title = {Numerical ranges of an operator on an indefinite inner product space},
     journal = {The electronic journal of linear algebra},
     publisher = {mathdoc},
     volume = {1},
     year = {1996},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/ELA_1996__1__a5/}
}