“…They also compared the relative importance of the MPS freezing parameters in influencing the total cost and schedule instability of the system. Sridharan and Berry (1990a), LaForge (1990, 1994), Lin and Krajewski (1992) extended the studies by Sridharan et al (1987Sridharan et al ( , 1988 from the case of deterministic demand to the case of demand uncertainty by introducing forecasting errors into the system. Lee (1993, 1996) and Zhao and Lam (1997) extended the studies by Sridharan et al (1987Sridharan et al ( , 1988) from single-level systems to multilevel MRP systems and found that some findings in single-level systems cannot be generalised to multi-level systems.…”