Contribution of the "hanged" diagrams into the reaction $np \to np \pi^+   \pi^-$
  The contribution of "hanged" diagrams into the reaction $np \rightarrow np \pi^+ \pi^-$ was considered. It was shown that taking into account of these diagrams permits to get better description of the effective mass spectrum of $\pi^+\pi^-$-combinations. 
A.P. Jerusalimov
nucl-th hep-ph