@article{AIHPC_1997__14_1_103_0,
     author = {Chang, K. C. and Liu, J. Q. and Liu, M. J.},
     title = {Nontrivial periodic solutions for strong resonance hamiltonian systems},
     journal = {Annales de l'I.H.P. Analyse non lin\'eaire},
     pages = {103--117},
     publisher = {Gauthier-Villars},
     volume = {14},
     number = {1},
     year = {1997},
     mrnumber = {1437190},
     zbl = {0881.34061},
     language = {en},
     url = {http://www.numdam.org/item/AIHPC_1997__14_1_103_0/}
}