@article{AIF_1976__26_1_141_0, author = {Sj\"ostrand, Johannes}, title = {Propagation of singularities for operators with multiple involutive characteristics}, journal = {Annales de l'Institut Fourier}, pages = {141--155}, publisher = {Institut Fourier}, volume = {26}, number = {1}, year = {1976}, doi = {10.5802/aif.602}, zbl = {0313.58021}, mrnumber = {54 #13285}, language = {en}, url = {http://www.numdam.org/articles/10.5802/aif.602/} }