@article{ETNA_2004__17__a12,
     author = {Psarrakos, Panayiotis J.},
     title = {On the estimation of the $q$-numerical range of monic matrix polynomials},
     journal = {Electronic transactions on numerical analysis},
     pages = {1--10},
     publisher = {mathdoc},
     volume = {17},
     year = {2004},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/ETNA_2004__17__a12/}
}