@article{AL_1993_32_3_a2,
     author = {Yu. L. Ershov},
     title = {Boolean families of valuation {rings.~II}},
     journal = {Algebra i logika},
     pages = {261--266},
     publisher = {mathdoc},
     volume = {32},
     number = {3},
     year = {1993},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/AL_1993_32_3_a2/}
}