@article{10_4064_cm_39_1_81_86,
     author = {H. H. Pu and H. W. Pu},
     title = {An approximative generalization of {Zahorski's} theorem on derivative},
     journal = {Colloquium Mathematicum},
     pages = {81--86},
     publisher = {mathdoc},
     volume = {39},
     number = {1},
     year = {1978},
     doi = {10.4064/cm-39-1-81-86},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.4064/cm-39-1-81-86/}
}