@article{10_14708_cm_v12i1_5640,
     author = {Z. Cybertowic},
     title = {On some approximation problems},
     journal = {Commentationes Mathematicae},
     pages = { 61--74},
     publisher = {mathdoc},
     volume = {12},
     number = {1},
     year = {1968},
     doi = {10.14708/cm.v12i1.5640},
     language = {pl},
     url = {http://geodesic.mathdoc.fr/articles/10.14708/cm.v12i1.5640/}
}