Shafer, Douglas S.; Zegeling, André Geometry of cycles in quadratic systems. (English) Zbl 1043.34030 Qual. Theory Dyn. Syst. 3, No. 1, 251-274 (2002). Reviewer: Alexander Grin (Grodno) MSC: 34C05 34C07 34A26 PDFBibTeX XMLCite \textit{D. S. Shafer} and \textit{A. Zegeling}, Qual. Theory Dyn. Syst. 3, No. 1, 251--274 (2002; Zbl 1043.34030) Full Text: DOI
Shafer, Douglas S.; Zegeling, André Vertices of planar curves under the action of linear transformations. (English) Zbl 1011.53002 J. Geom. 73, No. 1-2, 148-175 (2002). Reviewer: Rolf Walter (Dortmund) MSC: 53A04 53A15 53A20 PDFBibTeX XMLCite \textit{D. S. Shafer} and \textit{A. Zegeling}, J. Geom. 73, No. 1--2, 148--175 (2002; Zbl 1011.53002) Full Text: DOI
Shafer, Douglas S.; Zegeling, André Any two quadratic cycles can be connected with a smooth arc. (English. Abridged French version) Zbl 0945.34019 C. R. Acad. Sci., Paris, Sér. I, Math. 330, No. 1, 35-40 (2000). Reviewer: C.P.Han (Arlington) MSC: 34C07 PDFBibTeX XMLCite \textit{D. S. Shafer} and \textit{A. Zegeling}, C. R. Acad. Sci., Paris, Sér. I, Math. 330, No. 1, 35--40 (2000; Zbl 0945.34019) Full Text: DOI
Shafer, Douglas S.; Wu, Xiaonan; Zegeling, André A numerical approach to bifurcations from quadratic centers. (English) Zbl 0860.65061 J. Math. Anal. Appl. 202, No. 1, 90-107 (1996). Reviewer: M.Gousidou-Koutita (Thessaloniki) MSC: 65L05 34C05 34C23 37-XX PDFBibTeX XMLCite \textit{D. S. Shafer} et al., J. Math. Anal. Appl. 202, No. 1, 90--107 (1996; Zbl 0860.65061) Full Text: DOI
Shafer, Douglas S.; Zegeling, André Bifurcation of limit cycles from quadratic centers. (English) Zbl 0833.34029 J. Differ. Equations 122, No. 1, 48-70 (1995). Reviewer: Yu.V.Rogovchenko (Firenze) MSC: 34C05 34C23 PDFBibTeX XMLCite \textit{D. S. Shafer} and \textit{A. Zegeling}, J. Differ. Equations 122, No. 1, 48--70 (1995; Zbl 0833.34029) Full Text: DOI