Vulpe, N. I. Gram’s theorem for differential systems. (Russian) Zbl 0548.34050 Mat. Issled. 77, 40-44 (1984). Gram’s theorem for two-dimensional differential systems is proved. Furthermore by means of the Capelli identity it is shown, that for qualitative investigations of two-dimensional differential systems it is already sufficient to study the polynomial centro-affine comitants depending on only one vector. Reviewer: K.Barckow MSC: 34C99 Qualitative theory for ordinary differential equations Keywords:Gram’s theorem; two-dimensional differential systems; Capelli identity; polynomial centro-affine comitants PDFBibTeX XMLCite \textit{N. I. Vulpe}, Mat. Issled. 77, 40--44 (1984; Zbl 0548.34050) Full Text: EuDML