@article{PORMA_2006__63_4_54015,
     author = {Ocalan, Ozkan},
     title = {Oscillation of difference equations with variable coefficients.},
     journal = {Portugaliae mathematica},
     pages = {407--414},
     publisher = {mathdoc},
     volume = {63},
     number = {4},
     year = {2006},
     zbl = {1135.39005},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/PORMA_2006__63_4_54015/}
}