@article{SM_2012_203_2_a5,
     author = {P. E. Ryabov and M. P. Kharlamov},
     title = {Classification of  singularities in the problem of motion of the {Kovalevskaya} top in a~double force field},
     journal = {Sbornik. Mathematics},
     pages = {257--287},
     publisher = {mathdoc},
     volume = {203},
     number = {2},
     year = {2012},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/SM_2012_203_2_a5/}
}