@article{PMF_1915_26_1_a5,
     author = {Sierpi\'nski, Wac{\l}aw},
     title = {O zwi\k{a}zku mi\k{e}dzy istnieniem granicy $lim_{\ensuremath{\Delta}x=0} {\frac{\ensuremath{\Delta}{\texttwosuperior}f(x)}{\ensuremath{\Delta}x{\texttwosuperior}}}$ a ci\k{a}g{\l}o\'sci\k{a} funkcyi f(x)},
     journal = {Prace Matematyczno-Fizyczne},
     pages = {121--129},
     publisher = {mathdoc},
     volume = {26},
     number = {1},
     year = {1915},
     language = {pl},
     url = {http://geodesic.mathdoc.fr/item/PMF_1915_26_1_a5/}
}