@article{10_4064_ap_6_1_74_81,
     author = {Z. Opial},
     title = {Nouvelles remarques sur l'\'equation diff\'erentielle u'' + a(t)u = 0},
     journal = {Annales Polonici Mathematici},
     pages = {74--81},
     publisher = {mathdoc},
     volume = {6},
     number = {1},
     year = {1959},
     doi = {10.4064/ap-6-1-74-81},
     language = {fr},
     url = {http://geodesic.mathdoc.fr/articles/10.4064/ap-6-1-74-81/}
}