The existence of periodic solutions for nonlinear systems of first-order differential equations at resonance
2000 ◽
Vol 21
(11)
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pp. 1282-1291
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1984 ◽
Vol 15
(3)
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pp. 221-232
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2003 ◽
Vol 52
(4)
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pp. 1095-1109
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2012 ◽
Vol 86
(2)
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pp. 327-338
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1978 ◽
Vol 82
(1-2)
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pp. 95-106
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2012 ◽
Vol 6
(2)
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pp. 159-173