Periodic Solutions of Differential and Difference Systems with Pendulum-Type Nonlinearities: Variational Approaches
2005 ◽
Vol 11
(13)
◽
pp. 1109-1118
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2012 ◽
Vol 18
(10)
◽
pp. 1623-1647
◽
2007 ◽
Vol 334
(1)
◽
pp. 738-752
◽
2015 ◽
Vol 22
(2)
◽
pp. 306-315
◽