@article{10_21136_CPM_1985_118248,
     author = {Pt\'ak, Vlastimil},
     title = {Extremal operators and oblique projections},
     journal = {\v{C}asopis pro p\v{e}stov\'an{\'\i} matematiky},
     pages = {343--350},
     publisher = {mathdoc},
     volume = {110},
     number = {4},
     year = {1985},
     doi = {10.21136/CPM.1985.118248},
     mrnumber = {820323},
     zbl = {0611.47022},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.21136/CPM.1985.118248/}
}