R. G, N. Rajan.R.R, J. Aultrin.K.S, and P. P, “Optimization of Machining Characteristics of Hybrid Composites Using Grey Relational Technique”, IJET, vol. 7, no. 3.1, pp. 158–161, Aug. 2018, doi: 10.14419/ijet.v7i3.1.17077.