@article{SF_1986__34_134838,
     author = {G. Greiner and I. Becker},
     title = {On the modulus of one-parameter semigroups.},
     journal = {Semigroup forum},
     pages = {185--202},
     publisher = {mathdoc},
     volume = {34},
     year = {1986},
     zbl = {0635.47036},
     url = {http://geodesic.mathdoc.fr/item/SF_1986__34_134838/}
}