Nijmegen Soft-Core Potential Including Two-Meson Exchange
  We report on the progress of the construction of the extended soft-core (ESC) Nijmegen potential. Next to the standard one-boson-exchange parts, the model includes the pion-meson-exchange potentials due to the parallel and crossed-box diagrams, as well as the one-pair and two-pair diagrams, vertices for which can be identified with similar interactions appearing in chiral-symmetric Lagrangians. Although the ESC potential is still under construction, it already gives an excellent description of all $N\!N$ scattering data below 350 MeV with $\chi^{2}/{\rm datum}=1.3$. 
V.G.J. Stoks and Th.A. Rijken