As far as future work is concerned, the current model can be extended in a number of important ways. First of all, it can
be strengthened by the integration of both forward and reverse logistics, seeing as both can share a number of resources such as transportation and warehouse capacities in a closed-loop network model and by considering different transportation modes such as trains, trucks, and ships. Integration could also occur on another note, such as between location and inventory, as seen in the works of [34–36,3 or routing and inventory decisions, based on the works of [37,39]. Another interesting approach would be to choose among a series of various contracts for outsourcing transportation. Furthermore, the model can be customized for different problems, in order to generate problem specific results for higher value practical applicability in a larger number of industries. Finally, certain factors can be modeled as stochastic parameters, to account for uncertainty in the model.