Chiral expansion of the nucleon mass to order q^6
  We present the results of a complete two-loop calculation at order q^6 of the nucleon mass in manifestly Lorentz-invariant chiral perturbation theory. The renormalization is performed using the reformulated infrared renormalization, which allows for the treatment of two-loop integrals while preserving all relevant symmetries, in particular chiral symmetry. 
M. R. Schindler, D. Djukanovic, J. Gegelia, S. Scherer