Abstract
For holomorphic Liénard equations, necessary and sufficient conditions for the existence of a center and an isochronous center are obtained without calculating the focus quantities and the isochronicity constants.
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Amel’kin, V.V., Rudenok, A.E. Centers and Isochronous Centers of Liénard Systems. Diff Equat 55, 283–293 (2019). https://doi.org/10.1134/S0012266119030017
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DOI: https://doi.org/10.1134/S0012266119030017