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机译:The Elusive Liapunov Periodic Solutions
Univ Cincinnati, Dept Math Sci, Cincinnati, OH 45221 USA;
Univ Publ Navarra, Dept Ingn Matemat & Informat, Pamplona 31006, Spain;
Liapunov center theorem; Periodic solutions; Hamiltonian systems in resonance; Reduced space; Orbit space; Orbifold; Singular reduction;