On the use of the Operator Product Expansion to constrain the hadron   spectrum
  We call into question a recently proposed idea on how the short-distance behavior of QCD correlation functions constrains hadronic states to become degenerate parity eigenstates as one goes up in the spectrum. In particular, we point out that the sum rules which have been proposed in this context are in general regulator dependent, and thus ill-defined. 
Maarten Golterman (SFSU, San Francisco) and Santiago Peris (UAB and   IFAE, Barcelona)