@article{MM2_1982__39_154890,
     author = {Michael Langenbruch},
     title = {Differentiability and growth of solutions of partial differential equations.},
     journal = {Manuscripta mathematica},
     pages = {297--312},
     publisher = {mathdoc},
     volume = {39},
     year = {1982},
     zbl = {0534.35023},
     url = {http://geodesic.mathdoc.fr/item/MM2_1982__39_154890/}
}