@article{AIF_1961__11__477_0,
     author = {H\"ormander, Lars},
     title = {Hypoelliptic differential operators},
     journal = {Annales de l'Institut Fourier},
     pages = {477--492},
     publisher = {Institut Fourier},
     address = {Grenoble},
     volume = {11},
     year = {1961},
     doi = {10.5802/aif.117},
     zbl = {0099.30101},
     mrnumber = {23 #A3368},
     language = {en},
     url = {https://aif.centre-mersenne.org/articles/10.5802/aif.117/}
}