@article{AM2_1985__29_137090,
     author = {Chun-San Lee and Sen-Yen Shaw},
     title = {Representation formulas for cosine and sine functions of operators.},
     journal = {Aequationes mathematicae},
     pages = {162--171},
     publisher = {mathdoc},
     volume = {29},
     year = {1985},
     zbl = {0591.47028},
     url = {http://geodesic.mathdoc.fr/item/AM2_1985__29_137090/}
}