@article{AL_2013_52_2_a6,
     author = {S. O. Speranskii},
     title = {Collapsing probabilistic {hierarchies.~I}},
     journal = {Algebra i logika},
     pages = {236--254},
     publisher = {mathdoc},
     volume = {52},
     number = {2},
     year = {2013},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/AL_2013_52_2_a6/}
}