@article{PMIHES_1990__71__105_0,
     author = {Franks, John},
     title = {Periodic points and rotation numbers for area preserving diffeomorphisms of the plane},
     journal = {Publications Math\'ematiques de l'IH\'ES},
     pages = {105--120},
     year = {1990},
     publisher = {Institut des Hautes Etudes Scientifiques},
     volume = {71},
     mrnumber = {1079645},
     zbl = {0721.58031},
     language = {en},
     url = {https://www.numdam.org/item/PMIHES_1990__71__105_0/}
}