Abstract
It is proved that the quadratic system with a weak focus and a strong focus has a unique limit cycle around one of the two foci, if there exists simultaneously limit cycles around each of the two foci for the system.
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References
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Supported by NSFC(19671071) and Zhejiang Provinical Natural Sciences Foundation
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Pingguang, Z. Quadratic systems with a weak focus and a strong focus. Appl. Math. Chin. Univ. 14, 7–14 (1999). https://doi.org/10.1007/s11766-999-0049-3
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DOI: https://doi.org/10.1007/s11766-999-0049-3