@article{10_4064_ap_17_2_147_154,
     author = {S. S\k{e}dziwy},
     title = {On periodic solutions of a certain third-order non-linear differential equation},
     journal = {Annales Polonici Mathematici},
     pages = {147--154},
     publisher = {mathdoc},
     volume = {17},
     number = {2},
     year = {1965},
     doi = {10.4064/ap-17-2-147-154},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.4064/ap-17-2-147-154/}
}