@article{MAN_1991__291_1_164878,
     author = {F. Andreu and J. Mart{\'\i}nez and J.M. Maz\'on},
     title = {A spectral mapping theorem for perturbed strongly continuous semigroups.},
     journal = {Mathematische Annalen},
     pages = {453--462},
     publisher = {mathdoc},
     volume = {291},
     number = {1},
     year = {1991},
     zbl = {0787.47033},
     url = {http://geodesic.mathdoc.fr/item/MAN_1991__291_1_164878/}
}