A comment on Chang and Dye (1999): EOQ model for deteriorating items with time-varying demand and partial backlogging

In a recent article Chang and Dye considered an EOQ model for deteriorating items with time-varying demand and partial backlogging over a ®nite planning horizon. The highlight of their model is that the backlogging rate, during the shortage period, is not ®xed but variable and is dependent on the length of the waiting time for the next replenishment. They obtained an optimal replenishment policy for the inventory system by de®ning the backlogging rate to be 1=…1‡ a…ti ÿ t††, siÿ1 4 t 4 ti, where the backlogging parameter a > 0, siÿ1 ˆ the time at which shortages start during the ith cycle and ti ˆ the time at which the ith replenishment is made. They also cited four numerical examples to illustrate the developed model. We noticed the following typographical errors in the paper.