@article{SF_1990__41_2_135057,
     author = {T. Papazyan},
     title = {Filters and semigroup properties.},
     journal = {Semigroup forum},
     pages = {329--338},
     publisher = {mathdoc},
     volume = {41},
     number = {2},
     year = {1990},
     zbl = {0702.22005},
     url = {http://geodesic.mathdoc.fr/item/SF_1990__41_2_135057/}
}