The Existence of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M1"><mml:mi>n</mml:mi></mml:math> Periodic Solutions on One Element <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M2"><mml:mi>n</mml:mi></mml:math>-Degree Polynomial Differential Equation
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