Toy Model for Pion Production in Nucleon-Nucleon Collisions
  We develop a toy model of pion production in nucleon-nucleon collisions that reproduces some of the features of the chiral Lagrangian calculations. We calculate the production amplitude and examine some common approximations. 
C. Hanhart, G.A. Miller, F. Myhrer, T. Sato, and U. van Kolck