Periodic solutions of arbitrary period, variational methods
2013 ◽
Vol 394
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pp. 92-95
2005 ◽
Vol 1065
(1)
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pp. 414-428
2003 ◽
Vol 23
(6)
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pp. 1691-1715
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1986 ◽
Vol 34
(2)
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pp. 253-265
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