Naftalevich, A. Positive semidefinite polynomials and sums of squares. (English) Zbl 0762.11018 Pure Appl. Math. Sci. 35, No. 1-2, 1-11 (1992). The paper considers the question of Hilbert, whether a positive semidefinite real polynomial of two real variables is a sum of squares. Hilbert’s answer and later refinements by Choi, Lam, Reznick and Rosenberg are partially proved and refined further. Reviewer: M.Peters (Münster) MSC: 11E76 Forms of degree higher than two 11E25 Sums of squares and representations by other particular quadratic forms 26C99 Polynomials, rational functions in real analysis Keywords:positive semidefinite real polynomial; sum of squares PDFBibTeX XMLCite \textit{A. Naftalevich}, Pure Appl. Math. Sci. 35, No. 1--2, 1--11 (1992; Zbl 0762.11018)