@article{RSMUP_1984__72__203_0,
     author = {Omari, Pierpaolo and Zanolin, Fabio},
     title = {Periodic solutions of {Li\'enard} equations},
     journal = {Rendiconti del Seminario Matematico della Universit\`a di Padova},
     pages = {203--230},
     publisher = {Seminario Matematico of the University of Padua},
     volume = {72},
     year = {1984},
     mrnumber = {778342},
     zbl = {0584.34045},
     language = {en},
     url = {http://www.numdam.org/item/RSMUP_1984__72__203_0/}
}