“…Two-layer LRPs solve three problems (Hamidi et al, , 2012a(Hamidi et al, , 2012b: 1) location problem: given a series of candidate locations, how many depots should exist and where should they be placed?, 2) allocation problem: which customers should be assigned to which depot?, and 3) routing problem: how many tours are needed for each depot, which customers should be served on each tour, and what is the order of customers on each tour?. In this section some of the two-layer LRPs are reviewed.…”