@article{ARM_1976__12_2_a1,
     author = {Mawhin, Jean},
     title = {Contractive mappings and periodically perturbed conservative systems},
     journal = {Archivum mathematicum},
     pages = {67--73},
     publisher = {mathdoc},
     volume = {12},
     number = {2},
     year = {1976},
     mrnumber = {0437858},
     zbl = {0353.47034},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/ARM_1976__12_2_a1/}
}