@article{MZ_1930__31_168208,
     author = {A. Haar},
     title = {\"Uber die {Multiplikationstabelle} der orthogonalen {Funktionensysteme}},
     journal = {Mathematische Zeitschrift},
     pages = {769--798},
     publisher = {mathdoc},
     volume = {31},
     year = {1930},
     zbl = {56.0942.01},
     url = {http://geodesic.mathdoc.fr/item/MZ_1930__31_168208/}
}