On inverse DEA model:The case of variable returns to scale

This article points out some mathematical mistakes and ambiguities of the published paper by Lertworasirikul et al. (2011).The published paper by Lertworasirikul et al. (2011) is clarified by proposing a correct form of MOLP and its usage.A theorem is proposed that revises the aforementioned mistakes. Lertworasirikul et al. (2011) proposed an inverse BCC model for the case of VRS. They used an MOLP model to assist them in the process of finding inputs. The proof of the main theorem contains considerable mistakes which invalidate the proof. Moreover, there are some ambiguities about the use of MOLP. The current article points out the drawbacks of Lertworasirikul et al. (2011) and then corrects the use of MOLP in a proposed inverse BCC model. This commentary continues with a revision of the aforementioned theorem with a valid proof. The proposed proof is entirely different from and simpler than Lertworasirikul et als. (2011). A numerical example illustrates the proposed models.