@article{SM_1996_187_4_a1,
     author = {V. S. Matveev},
     title = {Integrable {Hamiltonian} system with two degrees of freedom. {The~topological} structure of saturated neighbourhoods of points of focus-focus and saddle-saddle type},
     journal = {Sbornik. Mathematics},
     pages = {495--524},
     publisher = {mathdoc},
     volume = {187},
     number = {4},
     year = {1996},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/SM_1996_187_4_a1/}
}