@article{SL_1958-1959__2__A8_0,
     author = {Zerner, Martin},
     title = {\'Equations aux d\'eriv\'ees partielles dont les solutions sont ind\'efiniment d\'erivables (hypoellipticit\'e)},
     journal = {S\'eminaire Lelong. Analyse},
     note = {talk:12},
     pages = {1--8},
     publisher = {Secr\'etariat math\'ematique},
     volume = {2},
     year = {1958-1959},
     language = {fr},
     url = {http://archive.numdam.org/item/SL_1958-1959__2__A8_0/}
}