@article{SF_1997__54_2_135519,
     author = {D. Song},
     title = {A note on the growth bound of {Co-semigroups.}},
     journal = {Semigroup forum},
     pages = {190--198},
     publisher = {mathdoc},
     volume = {54},
     number = {2},
     year = {1997},
     zbl = {0892.47045},
     url = {http://geodesic.mathdoc.fr/item/SF_1997__54_2_135519/}
}