@article{MZM_2011_89_2_a4,
     author = {P. Voj\v{c}\'ak},
     title = {A {Characterization} of {Hyers--Lang} {Differentiability} in {Terms} of a {Tangent} {Cone}},
     journal = {Matemati\v{c}eskie zametki},
     pages = {214--225},
     publisher = {mathdoc},
     volume = {89},
     number = {2},
     year = {2011},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MZM_2011_89_2_a4/}
}