@article{AUPO_1990__29_1_a6,
     author = {Rach\r{u}nkov\'a, Irena},
     title = {Periodic boundary value problems for second order differential equations},
     journal = {Acta Universitatis Palackianae Olomucensis. Facultas Rerum Naturalium. Mathematica},
     pages = {83--91},
     publisher = {mathdoc},
     volume = {29},
     number = {1},
     year = {1990},
     mrnumber = {1144833},
     zbl = {0752.34021},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/AUPO_1990__29_1_a6/}
}