Within the frame work of time independent non-relativistic quantum scattering theory the importance of the nucleon-nucleon, nucleus-nucleus scattering by additive interactions have been discussed. Within the formalism of separable model electromagnetic-distorted nuclear scattering has been treated to construct closed form analytical expressions for off-shell quantities in their maximal reduced form via different approaches to the problem and make them amenable to numerical treatment. The integral representations for on- and off-shell Jost functions for all partial waves in the representation...