@article{CM_1938__5__354_0,
     author = {Freudenthal, Hans},
     title = {Die Haarschen Orthogonalsysteme von Gruppencharakteren im Lichte der Pontrjaginschen Dualit\"atstheorie},
     journal = {Compositio Mathematica},
     pages = {354--356},
     publisher = {Johnson Reprint Corporation},
     volume = {5},
     year = {1938},
     zbl = {0018.39204},
     language = {de},
     url = {http://www.numdam.org/item/CM_1938__5__354_0/}
}

Freudenthal, Hans. Die Haarschen Orthogonalsysteme von Gruppencharakteren im Lichte der Pontrjaginschen Dualitätstheorie. Compositio Mathematica, Tome 5 (1938) , pp. 354-356. http://www.numdam.org/item/CM_1938__5__354_0/