@article{oai:tsukuba.repo.nii.ac.jp:00018690,
author = {木下, 保 and Ancona, Piero D' and Kinoshita, Tamotu and Spagnolo, Sergio},
issue = {4},
journal = {Osaka journal of mathematics},
month = {Dec},
note = {We study the wellposedness in the Gevrey classes $\gamma^{s}$ and in $C^{\infty}$ of the Cauchy problem for 2 by 2 weakly hyperbolic systems. In this paper we shall give some conditions to the case that the characteristic roots oscillate rapidly and vanish at an infinite number of points.},
pages = {921--939},
title = {On the 2 by 2 weakly hyperbolic systems},
volume = {45},
year = {2008}
}