@article{MM2_1988__62_3_155336,
     author = {Vlastimil Pt\'ak},
     title = {An operator-theoretic approach to theorems of the {Pick-Nevanlinna} and carath\'eodory types.},
     journal = {Manuscripta mathematica},
     pages = {131--144},
     publisher = {mathdoc},
     volume = {62},
     number = {3},
     year = {1988},
     zbl = {0659.47022},
     url = {http://geodesic.mathdoc.fr/item/MM2_1988__62_3_155336/}
}