@article{MAN_1917__78_158775,
     author = {E. Hecke},
     title = {\"Uber orthogonal-invariante {Integralgleichungen.}},
     journal = {Mathematische Annalen},
     pages = {398--404},
     publisher = {mathdoc},
     volume = {78},
     year = {1917},
     zbl = {46.0632.02},
     url = {http://geodesic.mathdoc.fr/item/MAN_1917__78_158775/}
}