Acquistapace F, Broglia F, F. Fernando J. On Hilbert’s 17th problem and Pfister’s multiplicative formulae for the ring of real analytic functions. Annali Scienze [Internet]. 2014Jun.16 [cited 2026Feb.20];13(2):333-69. Available from: https://journals.sns.it/index.php/annaliscienze/article/view/340