@article{TIMM_2016_22_3_a21,
     author = {E. G. Pytkeev and A. G. Chentsov},
     title = {Open ultrafilters and separability with the use of the operation of closure},
     journal = {Trudy Instituta matematiki i mehaniki},
     pages = {212--225},
     publisher = {mathdoc},
     volume = {22},
     number = {3},
     year = {2016},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/TIMM_2016_22_3_a21/}
}