@article{MAN_1968__177_161702,
     author = {J.J. Sch\"affer},
     title = {A {Note} on {Systems} of {Linear} {Difference} {Equations.}},
     journal = {Mathematische Annalen},
     pages = {23--30},
     publisher = {mathdoc},
     volume = {177},
     year = {1968},
     zbl = {0159.12701},
     url = {http://geodesic.mathdoc.fr/item/MAN_1968__177_161702/}
}