@article{SF_1992__44_1_135159,
     author = {T. Xio and J. Liang},
     title = {Analyticity of the propagators of second order linear differential equations in {Banach} spaces.},
     journal = {Semigroup forum},
     pages = {356--363},
     publisher = {mathdoc},
     volume = {44},
     number = {1},
     year = {1992},
     zbl = {0782.47041},
     url = {http://geodesic.mathdoc.fr/item/SF_1992__44_1_135159/}
}