1. L. L. Bergeson, Pollut. Eng., vol. 28, no. 6, pp. 17960–18011 (1996).
2. U. Eko, J. Ilmu Adm. Dan Organ., vol. 15, no. 3, pp. 178–187 (2008).
3. Y. W. Purnomo, Sigma, vol. VI, no. 01, pp. 22–33 (2014).
4. A Fuzzy Logic Based Approach to Explore Manufacturing System Changeability Level Decisions
5. C. Skills, U. States, N. Child, and L. Behind, “21st Century Skills Assessment,” (2001).