@article{AM2_1988__36_2-3_137276,
     author = {Ioana Cionarescu and Carlos Lizama},
     title = {Spectral properties of cosine operator functions.},
     journal = {Aequationes mathematicae},
     pages = {80--98},
     publisher = {mathdoc},
     volume = {36},
     number = {2-3},
     year = {1988},
     zbl = {0675.47029},
     url = {http://geodesic.mathdoc.fr/item/AM2_1988__36_2-3_137276/}
}