@article{MAN_1924__91_159038,
     author = {L. Koschmieder},
     title = {\"Uber ein {Biorthogonalsystem} von {Polynomen} zweier {Ver\"anderlichen}},
     journal = {Mathematische Annalen},
     pages = {62--81},
     year = {1924},
     volume = {91},
     zbl = {50.0261.02},
     url = {http://geodesic.mathdoc.fr/item/MAN_1924__91_159038/}
}