@article{MZ_1990__203_3_174139,
     author = {Hermann Sohr and Jan Pr\"uss},
     title = {On {Operators} with {Bounded} {Imaginary} {Powers} in {Banach} {Spaces.}},
     journal = {Mathematische Zeitschrift},
     pages = {429--452},
     publisher = {mathdoc},
     volume = {203},
     number = {3},
     year = {1990},
     zbl = {0665.47015},
     url = {http://geodesic.mathdoc.fr/item/MZ_1990__203_3_174139/}
}