@article{ELA_2010__20__a30,
     author = {Henrion, Didier},
     title = {Semidefinite geometry of the numerical range},
     journal = {The electronic journal of linear algebra},
     pages = {322--332},
     publisher = {mathdoc},
     volume = {20},
     year = {2010},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/ELA_2010__20__a30/}
}