@article{ISU_2012_12_2_a2,
     author = {S. A. Kreis},
     title = {Frames and periodic groups of operators},
     journal = {Izvestiya of Saratov University. Mathematics. Mechanics. Informatics},
     pages = {14--18},
     publisher = {mathdoc},
     volume = {12},
     number = {2},
     year = {2012},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/ISU_2012_12_2_a2/}
}