In  John Burgess describes predicative versions of Frege's logic and poses the problem of finding their exact arithmetical strength. I prove here that PV, the simplest such theory, is equivalent to Robinson's arithmetical theory Q.
"Burgess' PV is Robinson's Q." J. Symbolic Logic 72 (2) 619 - 624, June 2007. https://doi.org/10.2178/jsl/1185803626