G. Jahanshahloo, F. Hosseinzadeh Lotfi, R. Maddahi, and Y. Jafari, “Efficiency and benchmarking in the presence of undesirable (bad) outputs: A DEA approach”, IJAMR, vol. 1, no. 2, pp. 178–188, May 2012, doi: 10.14419/ijamr.v1i2.44.