@article{PSMIR_1973___2_A7_0,
     author = {Zuily, Claude},
     title = {Hypoellipticit\'e des op\'erateurs diff\'erentiels du 2e ordre \`a coefficients r\'eels},
     journal = {Publications des s\'eminaires de math\'ematiques et informatique de Rennes},
     note = {talk:7},
     pages = {1--5},
     publisher = {D\'epartement de Math\'ematiques et Informatique, Universit\'e de Rennes},
     number = {2},
     year = {1973},
     language = {fr},
     url = {http://www.numdam.org/item/PSMIR_1973___2_A7_0/}
}