@article{CMUC_1998__39_3_a4, author = {Lemmert, Roland and Volkmann, Peter}, title = {On the positivity of semigroups of operators}, journal = {Commentationes Mathematicae Universitatis Carolinae}, pages = {483--489}, publisher = {mathdoc}, volume = {39}, number = {3}, year = {1998}, mrnumber = {1666770}, zbl = {0970.47026}, language = {en}, url = {http://geodesic.mathdoc.fr/item/CMUC_1998__39_3_a4/} }