@misc{Yang_Xiao-Song_On_2000,
 author={Yang, Xiao-Song},
 volume={48},
 editor={Polska Akademia Nauk.},
 number={2},
 copyright={Rights Reserved - Restricted Access},
 address={Warsaw},
 address={Warsaw},
 howpublished={online},
 year={2000},
 publisher={Polska Akademia Nauk. Centrum Upowszechniania Nauki.},
 language={eng},
 title={On existence of subharmonic orbits in perturbed Hamiltonian systems},
 type={Text},
}