@article{TMF_1987_73_1_a7,
     author = {R. Kh. Sabirov},
     title = {Convolution of the secular equation of perturbation theory for a~degenerate case},
     journal = {Teoreti\v{c}eska\^a i matemati\v{c}eska\^a fizika},
     pages = {79--84},
     publisher = {mathdoc},
     volume = {73},
     number = {1},
     year = {1987},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/TMF_1987_73_1_a7/}
}