@article{ARM_1998__34_1_a9,
     author = {G\'orniewicz, Lech},
     title = {Periodic problems for {ODEs} via multivalued {Poincar\'e} operators},
     journal = {Archivum mathematicum},
     pages = {93--104},
     publisher = {mathdoc},
     volume = {34},
     number = {1},
     year = {1998},
     mrnumber = {1629672},
     zbl = {0915.34029},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/ARM_1998__34_1_a9/}
}