Szulkin, A.: Hamiltonian systems with periodic nonlinearities.
(English).
In:
Kurzweil, Jaroslav (ed.): Equadiff 7.
Proceedings of the 7th Czechoslovak Conference on Differential Equations and Their Applications held in Prague, 1989.
BSB B.G. Teubner Verlagsgesellschaft, Leipzig, 1990.
pp. 131-134
