@article{UFA_2018_10_3_a5,
     author = {N. M. Poluboyarova},
     title = {On   instability of extremals of    potential energy functional},
     journal = {Ufa mathematical journal},
     pages = {77--85},
     publisher = {mathdoc},
     volume = {10},
     number = {3},
     year = {2018},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/UFA_2018_10_3_a5/}
}