@article{MAN_1959__137_160678,
     author = {H. Lenz},
     title = {Lineare {Halbgruppen} mit beschr\"ankten {Eigenwerten.}},
     journal = {Mathematische Annalen},
     pages = {150--166},
     publisher = {mathdoc},
     volume = {137},
     year = {1959},
     zbl = {0099.36702},
     url = {http://geodesic.mathdoc.fr/item/MAN_1959__137_160678/}
}