@article{TMF_1980_45_2_a4,
     author = {M. A. Braun and A. D. Gurchumeliya},
     title = {Relativistic adiabatic perturbation theory for degenerate levels},
     journal = {Teoreti\v{c}eska\^a i matemati\v{c}eska\^a fizika},
     pages = {199--209},
     publisher = {mathdoc},
     volume = {45},
     number = {2},
     year = {1980},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/TMF_1980_45_2_a4/}
}