@article{PMIHES_1973__42__121_0,
     author = {Schaeffer, David G.},
     title = {An index theorem for systems of difference operators on a half space},
     journal = {Publications Math\'ematiques de l'IH\'ES},
     pages = {121--127},
     publisher = {Institut des Hautes \'Etudes Scientifiques},
     volume = {42},
     year = {1973},
     mrnumber = {320807},
     zbl = {0274.47020},
     language = {en},
     url = {http://www.numdam.org/item/PMIHES_1973__42__121_0/}
}