@article{10_4064_ap_53_1_29_34,
     author = {Piotr Fija{\l}kowski},
     title = {On the equation x''(t) = {F(t,} x(t)) in the {Sobolev} space $H^1(R)$},
     journal = {Annales Polonici Mathematici},
     pages = {29--34},
     publisher = {mathdoc},
     volume = {53},
     number = {1},
     year = {1991},
     doi = {10.4064/ap-53-1-29-34},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.4064/ap-53-1-29-34/}
}