@article{10_21136_MB_1992_126064,
     author = {Medkov\'a, Dagmar},
     title = {On essential norm of the {Neumann} operator},
     journal = {Mathematica Bohemica},
     pages = {393--408},
     publisher = {mathdoc},
     volume = {117},
     number = {4},
     year = {1992},
     doi = {10.21136/MB.1992.126064},
     mrnumber = {1197288},
     zbl = {0773.31006},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.21136/MB.1992.126064/}
}