@article{MAN_1971__192_162173,
     author = {John N. WELCH},
     title = {Spectral {Properties} of a {Linear} {Operator} {Connected} with {Solutions} of {Linear} {Differential} {Equations} in {Banach} {Spaces.}},
     journal = {Mathematische Annalen},
     pages = {253--256},
     publisher = {mathdoc},
     volume = {192},
     year = {1971},
     zbl = {0206.13803},
     url = {http://geodesic.mathdoc.fr/item/MAN_1971__192_162173/}
}