A number of characteristics that significantly complicate production planning and control activities may be inferred from the research literature. Specifically, seven complicating characteristics have been proposed in various forms by researchers. No researcher identifies more than four of the complicating characteristics, and many of the characteristics are only mentioned in passing. The seven characteristics are (1) the uncertain timing and quantity of returns, (2) the need to balance returns with demands, (3) the dis-assembly of returned products, (4) the uncertainty in materials recovered from returned items, (5) the requirement for a reverse logistics network, (6) the complication of material matching restrictions, and (7) the problems of stochastic routing for materials for re-manufacturing operations and highly variable processing times. Table 2 shows each of the complicating characteristics investigated by research in specific production planning and control activities.