@article{oai:tsukuba.repo.nii.ac.jp:00017140, author = {Kinoshita, Tamotu}, issue = {1}, journal = {Tsukuba Journal of Mathematics}, month = {Jun}, pages = {241--271}, title = {On the wellposedness in the ultradifferentiable classes of the Cauchy problem for a weakly hyperbolic equation of second order}, volume = {22}, year = {1998} }