@article{SM_1996_187_2_a6,
     author = {I. V. Protasov},
     title = {Points of joint continuity for the~semigroup of ultrafilters on {an~Abelian} group},
     journal = {Sbornik. Mathematics},
     pages = {287--296},
     publisher = {mathdoc},
     volume = {187},
     number = {2},
     year = {1996},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/SM_1996_187_2_a6/}
}