Popa, M. N.; Sibirskij, K. S. Invariant lines of a general quadratic differential system. (Russian. English summary) Zbl 0915.34025 Bul. Acad. Ştiinţe Repub. Mold., Mat. 1991, No. 1(4), 77-80 (1991). Reviewer: K.R.Schneider (Berlin) MSC: 34C05 PDFBibTeX XMLCite \textit{M. N. Popa} and \textit{K. S. Sibirskij}, Bul. Acad. Științe Repub. Mold., Mat. 1991, No. 1(4), 77--80 (1991; Zbl 0915.34025)
Popa, M. N.; Sibirskij, K. S. Conditions for the existence of a homogeneous particular integral of a differential system. (English. Russian original) Zbl 0657.34003 Differ. Uravn. 23, No. 8, 1324-1331 (1987); translation from Differ. Equations 23, No. 8, 894-900 (1987). Reviewer: J.H.Tian MSC: 34A05 PDFBibTeX XMLCite \textit{M. N. Popa} and \textit{K. S. Sibirskij}, Differ. Uravn. 23, No. 8, 1324--1331 (1987; Zbl 0657.34003); translation from Differ. Equations 23, No. 8, 894--900 (1987)
Popa, M. N.; Sibirskij, K. S. Focal cyclicity of critical points of a differential system. (English. Russian original) Zbl 0632.34022 Differ. Equations 22, 1069-1074 (1986); translation from Differ. Uravn. 22, No. 9, 1539-1545 (1986). Reviewer: A.Reinfelds (Riga) MSC: 34C05 PDFBibTeX XMLCite \textit{M. N. Popa} and \textit{K. S. Sibirskij}, Differ. Equations 22, 1069--1074 (1986; Zbl 0632.34022); translation from Differ. Uravn. 22, No. 9, 1539--1545 (1986)
Popa, M. N.; Sibirskij, K. S. Affine classification of systems with quadratic nonlinearities and a nonunique canonical form. (English) Zbl 0412.34024 Differ. Equations 14, 732-735 (1978). MSC: 34C20 34A34 PDFBibTeX XMLCite \textit{M. N. Popa} and \textit{K. S. Sibirskij}, Differ. Equations 14, 732--735 (1978; Zbl 0412.34024)
Popa, M. N.; Sibirskij, K. S. Affine classification of a system with square non-linearities and ambiguous canonical form. (Russian) Zbl 0402.34026 Differ. Uravn. 14, 1028-1033 (1978). MSC: 34C20 PDFBibTeX XMLCite \textit{M. N. Popa} and \textit{K. S. Sibirskij}, Differ. Uravn. 14, 1028--1033 (1978; Zbl 0402.34026)
Kirnitskaya, Eh. F.; Popa, M. N.; Sibirskij, K. S. Neue Anwendungen affiner Invarianten eines quadratischen Differentialsystems. (Russian) Zbl 0354.34028 Mat. Issled. 10, No. 2(36), 137-149 (1975). MSC: 34C05 PDFBibTeX XMLCite \textit{Eh. F. Kirnitskaya} et al., Mat. Issled. 10, No. 2(36), 137--149 (1975; Zbl 0354.34028)