@article{AM2_1977__15_136658,
     author = {J.J. Koliha},
     title = {Convergence of an operator series. {(Short} {Communication).}},
     journal = {Aequationes mathematicae},
     pages = {303--304},
     publisher = {mathdoc},
     volume = {15},
     year = {1977},
     zbl = {0376.47011},
     url = {http://geodesic.mathdoc.fr/item/AM2_1977__15_136658/}
}