@article{MZ_1927__26_167914,
     author = {St. Kaczmarz},
     title = {\"Uber die {Summierbarkeit} der {Orthogonalreihen}},
     journal = {Mathematische Zeitschrift},
     pages = {99--105},
     publisher = {mathdoc},
     volume = {26},
     year = {1927},
     zbl = {53.0267.01},
     url = {http://geodesic.mathdoc.fr/item/MZ_1927__26_167914/}
}