@article{MAN_1974__209_162582,
     author = {M. Breuer and R.S. Butcher},
     title = {Fredholm {Theories} of {Mixed} {Type} with {Analytic} {Index} {Functions.}},
     journal = {Mathematische Annalen},
     pages = {31--42},
     publisher = {mathdoc},
     volume = {209},
     year = {1974},
     zbl = {0265.46057},
     url = {http://geodesic.mathdoc.fr/item/MAN_1974__209_162582/}
}