Description for the reactions a + b → c + d + e

A formalism for describing the reactions a+b→c+d+e is presented in detail and the experiments necessary for the reconstruction of the transition amplitude described. Experiments involving polarized targets are discussed carefully and a partial-wave analysis is made which is particularly suitable for application at low c.m. energies. It is shown that in order to resolve parity ambiguities it is necessary to observe the final particle polarizations.