@article{AM2_1980__21_182435,
     author = {G.F. Webb},
     title = {A representation formula for strongly continuous cosine families.},
     journal = {Aequationes mathematicae},
     pages = {251--256},
     publisher = {mathdoc},
     volume = {21},
     year = {1980},
     zbl = {0467.47037},
     url = {http://geodesic.mathdoc.fr/item/AM2_1980__21_182435/}
}