@article{AUPO_1991__30_1_a12,
     author = {Andres, Jan},
     title = {Periodic solutions of the third-order differential equation with right-hand side in the form of nonlinear restoring term plus general gradient-like part},
     journal = {Acta Universitatis Palackianae Olomucensis. Facultas Rerum Naturalium. Mathematica},
     pages = {143--148},
     publisher = {mathdoc},
     volume = {30},
     number = {1},
     year = {1991},
     mrnumber = {1166433},
     zbl = {0777.34029},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/AUPO_1991__30_1_a12/}
}