@article{AUPO_1991__30_1_a15,
     author = {Vl\v{c}ek, Vladim{\'\i}r},
     title = {Addendum to periodic solutions of a third-order nonlinear differential equation},
     journal = {Acta Universitatis Palackianae Olomucensis. Facultas Rerum Naturalium. Mathematica},
     pages = {189--202},
     publisher = {mathdoc},
     volume = {30},
     number = {1},
     year = {1991},
     mrnumber = {1166436},
     zbl = {0777.34032},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/AUPO_1991__30_1_a15/}
}