1. Vrana J. The four industrial revolutions. 2020. [Online]. Available: https://youtu.be/59SsqSWw4b0
2. Singh R. Purpose and pursuit of NDE 4.0. Mater Eval. 2020;78:784–93.
3. Singh R. NDE 4.0: the next revolution in nondestructive testing and evaluation: what and how? Mater Eval. 2019;77:45–50.
4. Klipfolio. What is a KPI? 2020. [Online]. Available: https://www.klipfolio.com/resources/articles/what-is-a-key-performance-indicator
5. Carr L, Ittner C. Measuring the cost of ownership 6.3. J Cost Manag. November/December 1992:42–51.