@article{PMF_1949_47_1_a4,
     author = {Biernacki, Mieczys{\l}aw},
     title = {Sur l'\'equation {\ensuremath{\Delta}y{\texttwosuperior}/h{\texttwosuperior}} + {A(x)y} = 0},
     journal = {Prace Matematyczno-Fizyczne},
     pages = {49--60},
     publisher = {mathdoc},
     volume = {47},
     number = {1},
     year = {1949},
     language = {fr},
     url = {http://geodesic.mathdoc.fr/item/PMF_1949_47_1_a4/}
}