@article{MZ_1920__8_167597,
     author = {O. Perron},
     title = {Zur {Theorie} der {Summengleichungen}},
     journal = {Mathematische Zeitschrift},
     pages = {159--170},
     publisher = {mathdoc},
     volume = {8},
     year = {1920},
     zbl = {47.0377.02},
     url = {http://geodesic.mathdoc.fr/item/MZ_1920__8_167597/}
}