@article{10_4064_ba55_1_7,
     author = {Antoni Wawrzy\'nczyk},
     title = {Schur {Lemma} and the {Spectral} {Mapping} {Formula}},
     journal = {Bulletin of the Polish Academy of Sciences. Mathematics},
     pages = {63--69},
     publisher = {mathdoc},
     volume = {55},
     number = {1},
     year = {2007},
     doi = {10.4064/ba55-1-7},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.4064/ba55-1-7/}
}