@article{IIMI_2006_36_2_a8,
     author = {A. S. Demyshev and V. I. Rodionov},
     title = {On equivalent definition of continuous differentiability},
     journal = {Izvestiya Instituta Matematiki i Informatiki Udmurtskogo Gosudarstvennogo Universiteta},
     pages = {39--42},
     publisher = {mathdoc},
     volume = {36},
     number = {2},
     year = {2006},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/IIMI_2006_36_2_a8/}
}