@article{MZM_2002_72_4_a5,
     author = {V. A. Romanov},
     title = {Nonequivalence of {Various} {Definitions} of {Differentiability} {Directions} for {Vector} {Measures}},
     journal = {Matemati\v{c}eskie zametki},
     pages = {528--534},
     publisher = {mathdoc},
     volume = {72},
     number = {4},
     year = {2002},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MZM_2002_72_4_a5/}
}