@article{MZ_1930__32_168230,
     author = {L, Schoenberg},
     title = {\"Uber variationsvermindernde lineare {Transformationen}},
     journal = {Mathematische Zeitschrift},
     pages = {321--328},
     year = {1930},
     volume = {32},
     zbl = {56.0106.06},
     url = {http://geodesic.mathdoc.fr/item/MZ_1930__32_168230/}
}