@article{SMJ2_2008_34_1_a6,
     author = {Nishitani, Tatsuo},
     title = {On {The} {Cauchy} {Problem} for {Non} {Effectively} {Hyperbolic} {Operators,} {The} {Ivrii-Petkov-H\"ormander} {Condition} and the {Gevrey} {Well} {Posedness}},
     journal = {Serdica Mathematical Journal},
     pages = {155--178},
     publisher = {mathdoc},
     volume = {34},
     number = {1},
     year = {2008},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/SMJ2_2008_34_1_a6/}
}