In the above formulation, objective function minimises the flow costs plus location costs (if included) for each time period plus the rearrangement costs between time periods. Constraint set 2 ensures that there is exactly one department from the proper time period for each location of each time period. Constraint set 3 ensures that each department of each time period is assigned to exactly one location of the proper time period. They modified various static layout algorithms to solve the dynamic version of the quadratic assignment model. In his two following papers Lacksonen [9,10] extended his previous DLP model by considering departments with unequal areas. He applied branch-and-bound routine and the cut tree algorithm to solve the mixed integer linear programming model. Balakrishnan et al. [11] considered budget constraints in their studies of DLP. They add the constraint of a budget for total rearrangement costs over the entire horizon and solve the problem using a constrained shortest path algorithm. Urban [12] proposed a heuristic algorithm that is based on the CRAFT (steepest descent pairwise interchange) procedure for DLP. Conway and Venkataramanan [13] applied genetic algorithms to solve DLP. Balakrishnan and Cheng [14] also recently proposed a genetic algorithm for DLP. A very good survey about DLP has recently been published by Balakrishnan and Cheng [15] that explains the state of the research on DLP. They gave detailed explanations about available algorithms on DLP along with their comparisons.