Topological phase portraits of planar semi-linear quadratic vector fields. (Q2744630)

Consider vector fields of the form NEWLINE\[NEWLINEX= (ax+ by,\,Ax+ By+ Cx^2+ Dxy+ Ey^2).NEWLINE\]NEWLINE The authors solve completely the topological classification of the phase portraits defined by \(X\). Moreover, they prove that quadratic systems of the class I in the Chinese classification base exact 50 different phase portraits which corrects a result in the book of \textit{Y. Ye} [Qualitative theory of polynomial differential systems. Modern Mathematics Series. Shanghai: Shanghai Scientific \& Technical Publishers (1995; Zbl 0854.34003)].