we may notice that by far the constraints and total costs are the same as the standard transportation model, except for notational differences. Now, let us examine transshipment nodes, which, in fact, make the transshipment problem different. A pure transshipment node only reroutes and redistributes goods to retailers according to retail demand without limits; therefore, the aggregate flow into each transshipment node equals the aggregate flow out of it. The flow into each transshipment nodeT can be expressed as: