@article{SF_1986__35_134878,
     author = {N. Sauer and J.E. Singleton},
     title = {Evolution operators related to semi-groups of class {(A).}},
     journal = {Semigroup forum},
     pages = {317--336},
     publisher = {mathdoc},
     volume = {35},
     year = {1986},
     zbl = {0617.47030},
     url = {http://geodesic.mathdoc.fr/item/SF_1986__35_134878/}
}