@article{CM_1970__22_1_67_0,
     author = {Westphal, U.},
     title = {Ein {Kalk\"ul} f\"ur gebrochene {Potenzen} infinitesimaler {Erzeuger} von {Halbgruppen} und {Gruppen} von {Operatoren.} {Teil} {I} : {Halbgruppenerzeuger}},
     journal = {Compositio Mathematica},
     pages = {67--103},
     publisher = {Wolters-Noordhoff Publishing},
     volume = {22},
     number = {1},
     year = {1970},
     mrnumber = {261395},
     zbl = {0194.15401},
     language = {de},
     url = {http://www.numdam.org/item/CM_1970__22_1_67_0/}
}