@article{10_4153_CJM_2004_007_4,
     author = {Li, Chi-Kwong and Sourour, Ahmed Ramzi},
     title = {Linear {Operators} on {Matrix} {Algebras} that {Preserve} the {Numerical} {Range,} {Numerical} {Radius} or the {States}},
     journal = {Canadian journal of mathematics},
     pages = {134--167},
     year = {2004},
     volume = {56},
     number = {1},
     doi = {10.4153/CJM-2004-007-4},
     url = {http://geodesic.mathdoc.fr/articles/10.4153/CJM-2004-007-4/}
}