Chiral aspects of hadron structure
  Chiral loop corrections for hadronic properties are considered in a constituent quark model. It is emphasized that the correct implementation of such corrections requires a sum over intermediate hadronic states. The leading non-analytic corrections are very important for baryon magnetic moments and explain the failure of the sum rule $(\mu_{\Sigma^{+}}+2\mu_{\Sigma^{-}})/\mu_{\Lambda}=-1$ predicted by the constituent quark model. 
A.W. Thomas and G. Krein