@article{JRAM_1967__227_150805,
     author = {H.O. Cordes},
     title = {On a generalized {Fredholm} theory.},
     journal = {Journal f\"ur die reine und angewandte Mathematik},
     pages = {121--149},
     publisher = {mathdoc},
     volume = {227},
     year = {1967},
     zbl = {0177.41002},
     url = {http://geodesic.mathdoc.fr/item/JRAM_1967__227_150805/}
}