Jianjun Lu Lu, J. J., & Fang, S. C. (2001). Solving nonlinear optimization problems with fuzzy relation equation constraints. FUZZY SETS AND SYSTEMS, 119(1), 1–20. https://doi.org/10.1016/S0165-0114(98)00471-0 Lu, J.-J., Brinkley, P., & Fang, S.-C. (1997). A fuzzy expert system model for RF receiver module testing. International Journal of Systems Science, 28(8), 791–798. https://doi.org/10.1080/00207729708929439