@article{ZNSL_1982_122_a5,
     author = {N. V. Ivanov},
     title = {Hielsen numbers of self-naps of surfaces},
     journal = {Zapiski Nauchnykh Seminarov POMI},
     pages = {56--65},
     publisher = {mathdoc},
     volume = {122},
     year = {1982},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/ZNSL_1982_122_a5/}
}