@article{SMJ2_1995_21_2_a0,
     author = {Christov, Ognyan and Dragnev, Dragomir},
     title = {Perturbations of {Systems} {Describing} the {Motion} of a {Particle} in {Central} {Fields}},
     journal = {Serdica Mathematical Journal},
     pages = {91--108},
     publisher = {mathdoc},
     volume = {21},
     number = {2},
     year = {1995},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/SMJ2_1995_21_2_a0/}
}