@article{ZNSL_1967_5_a3,
     author = {V. P. Il'in},
     title = {On a~class functions of several real variables},
     journal = {Zapiski Nauchnykh Seminarov POMI},
     pages = {110--168},
     publisher = {mathdoc},
     volume = {5},
     year = {1967},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/ZNSL_1967_5_a3/}
}