@article{PFMT_2012_2_a5,
     author = {E. M. Ovsiyuk and O. V. Veko and V. M. Red'kov},
     title = {Mueller semigroups of the rank 1 and 2},
     journal = {Problemy fiziki, matematiki i tehniki},
     pages = {34--40},
     publisher = {mathdoc},
     number = {2},
     year = {2012},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/PFMT_2012_2_a5/}
}