@article{AL_2012_51_2_a2,
     author = {Yu. L. Ershov},
     title = {A stability criterion},
     journal = {Algebra i logika},
     pages = {193--196},
     publisher = {mathdoc},
     volume = {51},
     number = {2},
     year = {2012},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/AL_2012_51_2_a2/}
}