@article{ASENS_1948_3_65__299_0,
     author = {Haag, Jules},
     title = {Sur l'existence et la stabilit\'e des solutions p\'eriodiques de certains syst\`emes diff\'erentiels},
     journal = {Annales scientifiques de l'\'Ecole Normale Sup\'erieure},
     pages = {299--335},
     publisher = {Elsevier},
     volume = {3e s{\'e}rie, 65},
     year = {1948},
     doi = {10.24033/asens.963},
     mrnumber = {11,111a},
     zbl = {0033.08402},
     language = {fr},
     url = {http://archive.numdam.org/articles/10.24033/asens.963/}
}