A comment on “An extended assignment problem considering multiple inputs and outputs”

This note shows that the data envelopment analysis (DEA) models formulated by Chen and Lu [L.H. Chen, H.W. Lu, An extended assignment problem considering multiple inputs and outputs, Appl. Math. Modell. 31 (2007) 2239–2248] are not correct. The enveloping form of the Chen and Lu formulation is studied and a simple example is presented to demonstrate the differences between the efficiency scores resulted of the Chen and Lu formulation, and the true ones.