@article{10_14708_cm_v9i2_5540,
     author = {K. Krzy\.zewski},
     title = {On the approximate derivative of superposition},
     journal = {Commentationes Mathematicae},
     pages = { 123--127},
     publisher = {mathdoc},
     volume = {9},
     number = {2},
     year = {1965},
     doi = {10.14708/cm.v9i2.5540},
     language = {pl},
     url = {http://geodesic.mathdoc.fr/articles/10.14708/cm.v9i2.5540/}
}