@article{CMUC_1987__28_1_a4,
     author = {Fonda, Alessandro and Zanolin, Fabio},
     title = {Periodic solutions to second order differential equations of {Li\'enard} type with jumping nonlinearities},
     journal = {Commentationes Mathematicae Universitatis Carolinae},
     pages = {33--41},
     publisher = {mathdoc},
     volume = {28},
     number = {1},
     year = {1987},
     mrnumber = {889766},
     zbl = {0625.34046},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/CMUC_1987__28_1_a4/}
}