@article{1174324326, author = {Colombini, Ferruccio and Nishitani, Tatsuo}, title = {Second order weakly hyperbolic operators with coefficients sum of powers of functions}, journal = {Osaka J. Math.}, volume = {44}, number = {1}, year = {2007}, pages = { 121-137}, language = {en}, url = {http://dml.mathdoc.fr/item/1174324326} }
Colombini, Ferruccio; Nishitani, Tatsuo. Second order weakly hyperbolic operators with coefficients sum of powers of functions. Osaka J. Math., Tome 44 (2007) no. 1, pp. 121-137. http://gdmltest.u-ga.fr/item/1174324326/