@article{RM_1987_42_4_a7,
     author = {M. B. Sevryuk},
     title = {On~invariant tori of reversible systems in the neighbourhood of an equilibrium position},
     journal = {Trudy Matematicheskogo Instituta imeni V.A. Steklova},
     pages = {147--148},
     publisher = {mathdoc},
     volume = {42},
     number = {4},
     year = {1987},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/RM_1987_42_4_a7/}
}