@article{RM_1989_44_2_a1,
     author = {A. D. Bruno},
     title = {Normalization of a {Hamiltonian} system near an invariant cycle or torus},
     journal = {Trudy Matematicheskogo Instituta imeni V.A. Steklova},
     pages = {53--89},
     publisher = {mathdoc},
     volume = {44},
     number = {2},
     year = {1989},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/RM_1989_44_2_a1/}
}