Integral representation for electromagnetic form factors of two-particle systems

It is assumed that the form factor of the connected part of the matrix element of the current of a two-particle system can be represented by the boundary values of functions that are holomorphic in a certain small neighborhood of the physical region. This assumption is used to derive an integral representation for the form factor of the two-particle system, expressing it in terms of the form factors of the particles constituting the system and the physical $S$-matrix. No assumptions are made concerning the dynamics of the two-particle system.