@article{IM2_1991_37_2_a5,
     author = {V. R. Ol'shevskii},
     title = {Change of {Jordan} structure of $G$-selfadjoint operators and selfadjoinl operator-functions under small perturbatios},
     journal = {Izvestiya. Mathematics },
     pages = {371--395},
     publisher = {mathdoc},
     volume = {37},
     number = {2},
     year = {1991},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/IM2_1991_37_2_a5/}
}