@article{PMF_1933_40_1_a7,
     author = {Biernacki, M.},
     title = {Sur l'\'equation diff\'erentielle {x''+A(t)x=0}},
     journal = {Prace Matematyczno-Fizyczne},
     pages = {163--171},
     publisher = {mathdoc},
     volume = {40},
     number = {1},
     year = {1933},
     language = {fr},
     url = {http://geodesic.mathdoc.fr/item/PMF_1933_40_1_a7/}
}