@article{GDZPPN001264354,
title = {Pertubation and comparison of cosine operator functions.},
journal = {Semigroup forum},
volume = {51},
year = {1995},
pages = {225-246},
zbl = {0828.47037},
url = {http://dml.mathdoc.fr/item/GDZPPN001264354}
}
Piskarev, S.; Shaw, S.YX. Pertubation and comparison of cosine operator functions.. Semigroup forum, Tome 51 (1995) pp. 225-246. http://gdmltest.u-ga.fr/item/GDZPPN001264354/