@article{PORMA_1978__37_3-4_115355,
     author = {Szmanda, B.},
     title = {Oscillation of solutions of second order difference equations},
     journal = {Portugaliae mathematica},
     pages = {251--254},
     publisher = {mathdoc},
     volume = {37},
     number = {3-4},
     year = {1978},
     mrnumber = {0633031},
     zbl = {0456.39003},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/PORMA_1978__37_3-4_115355/}
}