Relativistic Quark Model Calculation of the l1, l2 Coefficients of the   Chiral Lagrangian
  We briefly report on a relativistic quark model scheme to calculate the O(P^4) pion-pion vertex in the planar approximation and in the chiral limit. The calculation is reduced to the solution of simple integral equations (Bethe-Salpeter like) by an effective use of chiral Ward Identities. Specific model computations are provided. 
Felipe J. Llanes-Estrada and Pedro Bicudo