@article{RSM_2000__58_4_125122,
     author = {Rodino, Luigi and De Donno, Giuseppe},
     title = {Gevrey hypoellipticity for partial differential equations with characteristics of higher multiplicity.},
     journal = {Rendiconti del seminario matematico},
     pages = {435--448},
     publisher = {mathdoc},
     volume = {58},
     number = {4},
     year = {2000},
     zbl = {1072.35214},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/RSM_2000__58_4_125122/}
}