摘 要: | 1 IntroductionThere is almost no other type of algebraic curve which may be able tofOrm a separatrix cyc1e containing a fOcus fOr quadratic systern except para-bola, hyperbo1a, ellipse, parabola and straight line, two half lines and relativeequatorial arc, a class of cubic curve and two classes of quartic curve (see 1]for details). However, besides of these, there are many other types of algebraiccurves which may be able to fOrm a separatrix cycle fOr cubic system, fOr ex-ample, double foli…
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