@article{SM_2006_197_12_a4,
     author = {K. S. Kazarian},
     title = {On the {Ul'yanov} problem},
     journal = {Sbornik. Mathematics},
     pages = {1805--1826},
     publisher = {mathdoc},
     volume = {197},
     number = {12},
     year = {2006},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/SM_2006_197_12_a4/}
}