  Using the resonance model, which was successfully applied for the study of
the $pp{\to}p{\Lambda}K^+$ reaction, we investigate $NN{\to}N{\Sigma}K$
reactions that should provide cleaner information about resonance excitations
and meson exchange contributions. For this purpose we demonstrate that the
invariant mass distribution for the ${\Sigma}K$ system, as well as the Dalitz
plot for the $NN{\to}N{\Sigma}K$ reaction, provide direct information about the
${\Sigma}K$ production mechanism, which can be tested in the near future by
experiments at COSY.

Nuclear Theory