@article{ZNSL_1976_60_a9,
     author = {S. A. Norgela},
     title = {On the approximation of reduction classes of {RPC} by decidable classes},
     journal = {Zapiski Nauchnykh Seminarov POMI},
     pages = {103--108},
     publisher = {mathdoc},
     volume = {60},
     year = {1976},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/ZNSL_1976_60_a9/}
}