@article{CM_1940__7__372_0, author = {Sidon, S.}, title = {\"Uber Orthogonalsysteme}, journal = {Compositio Mathematica}, pages = {372--375}, publisher = {Johnson Reprint Corporation}, volume = {7}, year = {1940}, zbl = {0023.02503}, mrnumber = {1995}, language = {de}, url = {www.numdam.org/item/CM_1940__7__372_0/} }
Sidon, S. Über Orthogonalsysteme. Compositio Mathematica, Tome 7 (1940) , pp. 372-375. http://www.numdam.org/item/CM_1940__7__372_0/