@article{ZNSL_2012_399_a5,
     author = {A. A. Knop},
     title = {Diophantine hierarchy},
     journal = {Zapiski Nauchnykh Seminarov POMI},
     pages = {109--127},
     year = {2012},
     volume = {399},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/ZNSL_2012_399_a5/}
}