@article{MT_1987_9_a5,
     author = {E. P. Volokitin and S. A. Treskov},
     title = {A variant of the bifurcation of a fourfold equilibrium state with two zero eigenvalues},
     journal = {Matemati\v{c}eskie trudy},
     pages = {60--66},
     publisher = {mathdoc},
     volume = {9},
     year = {1987},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MT_1987_9_a5/}
}