@article{MAN_1962__145_160915,
     author = {J.J. Sch\"affer},
     title = {Linear {Differential} {Equations} and {Functional} {Analysis.} {VI.}},
     journal = {Mathematische Annalen},
     pages = {354--400},
     publisher = {mathdoc},
     volume = {145},
     year = {1962},
     zbl = {0099.32501},
     url = {http://geodesic.mathdoc.fr/item/MAN_1962__145_160915/}
}