On the expressive power of univariate equations over sets of natural numbers.

Alexander Okhotin Panos Rondogiannis On the expressive power of univariate equations over sets of natural numbers. 215-227 2008 IFIP TCS http://dx.doi.org/10.1007/978-0-387-09680-3_15 conf/ifipTCS/2008 db/conf/ifipTCS/ifipTCS2008.html#OkhotinR08