FOM: Simpson's book

[friedman@math.ohio-state.edu]

Insall <montez at rollanet.org> said:

> Matt Insall
> PS:  I know I should look it up myself,
> but I'll ask anyway.
> Does anyone know af a conservative,
> finitely axiomatizable extension of PA?
> 
Simpson's book, Subsystems of second order arithmetic: ACA_0 is a finitely 
axiomatizable conservative extension of PA. Unfortunately, Simpson's book is 
temporarily out of print. 



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