  In data envelopment analysis (DEA), the occurrence of multiple reference sets
is a crucial issue in identifying all the reference DMUs to a given decision
making unit (DMU). To resolve this difficulty, we introduce the useful notion
of maximal reference set (MRS) which contains all the reference DMUs. Based on
both primal and dual formulations, we then propose a new mixed integer linear
programming (MILP) based approach for determining the MRS. The proposed
approach is more general than the existing ones, and has several desirable
properties: (i) having a unified formulation, (ii) adaptable with different DEA
models, and (iii) compatible with both primal and dual forms of the DEA models.
Furthermore, our approach is made computationally effective by establishing a
LP-based procedure to treat with the primal-based MILP.
