@article{10_4064_sm158_1_2,
     author = {Fuad Kittaneh},
     title = {A numerical radius inequality and an estimate for the
 numerical radius of the {Frobenius} companion matrix},
     journal = {Studia Mathematica},
     pages = {11--17},
     year = {2003},
     volume = {158},
     number = {1},
     doi = {10.4064/sm158-1-2},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.4064/sm158-1-2/}
}