@article{AULFM_1992_05_a4,
     author = {{\L}azarow, Ewa},
     title = {The oscillatory behaviour of {I-approximate} derivatives},
     journal = {Acta Universitatis Lodziensis. Folia Mathematica},
     publisher = {mathdoc},
     volume = {05},
     year = {1992},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/AULFM_1992_05_a4/}
}