摘要
In this paper we will show that classes C1, C4, C9 and C14 in table 1 and classes 1, 2 and 12 in table 2 of Shi Songling [5] are not empty by constucting examples in these classes. Our results thus imply that there are at least 43 and at most 50 classes of structurally stable quadratic systems without limit cycles.
In this paper we will show that classes C1, C4, C9 and C14 in table 1 and classes 1, 2 and 12 in table 2 of Shi Songling [5] are not empty by constucting examples in these classes. Our results thus imply that there are at least 43 and at most 50 classes of structurally stable quadratic systems without limit cycles.
