@article{AL_2008_47_3_a0,
     author = {Yu. L. Ershov},
     title = {Stability preservation theorems},
     journal = {Algebra i logika},
     pages = {269--287},
     publisher = {mathdoc},
     volume = {47},
     number = {3},
     year = {2008},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/AL_2008_47_3_a0/}
}