@article{AM2_1975__12_136505,
     author = {Z. Ditzian},
     title = {Some {Remarks} on {Inequalities} of {Landau} and {Kolmogorov.}},
     journal = {Aequationes mathematicae},
     pages = {145--151},
     publisher = {mathdoc},
     volume = {12},
     year = {1975},
     zbl = {0309.47007},
     url = {http://geodesic.mathdoc.fr/item/AM2_1975__12_136505/}
}