@article{oai:tsukuba.repo.nii.ac.jp:00017234,
 author = {Yuzawa, Yasuo},
 issue = {2},
 journal = {Tsukuba Journal of Mathematics},
 month = {Dec},
 pages = {321--335},
 title = {Propagation of analyticity of solutions to the Cauchy problem for weakly hyperbolic semi-linear equations},
 volume = {25},
 year = {2001}
}