@article{ZNSL_2013_414_a6,
     author = {D. D. Kiselev and B. B. Lur'e},
     title = {Ultrasolvability and singularity in the embedding problem},
     journal = {Zapiski Nauchnykh Seminarov POMI},
     pages = {113--126},
     year = {2013},
     volume = {414},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/ZNSL_2013_414_a6/}
}