Di Nasso, Mauro; Forti, Marco Ultrafilter semirings and nonstandard submodels of the Stone-Čech compactification of the natural numbers. (English) Zbl 1079.16036 Blass, Andreas (ed.) et al., Logic and its applications. Result of the conference on logic and its applications in algebra and geometry, Ann Arbor, MI, USA, April 11–13, 2003 and the workshop on combinatorial set theory, excellent classes, and Schanuel conjecture, Ann Arbor, MI, USA, April 14–15, 2003. Providence, RI: American Mathematical Society (AMS) (ISBN 0-8218-3474-6/pbk). Contemporary Mathematics 380, 45-51 (2005). MSC: 16Y60 03H15 54D80 PDFBibTeX XMLCite \textit{M. Di Nasso} and \textit{M. Forti}, Contemp. Math. 380, 45--51 (2005; Zbl 1079.16036)
Benci, Vieri; Di Nasso, Mauro A purely algebraic characterization of the hyperreal numbers. (English) Zbl 1113.26028 Proc. Am. Math. Soc. 133, No. 9, 2501-2505 (2005). MSC: 26E35 16S60 54C40 PDFBibTeX XMLCite \textit{V. Benci} and \textit{M. Di Nasso}, Proc. Am. Math. Soc. 133, No. 9, 2501--2505 (2005; Zbl 1113.26028) Full Text: DOI