B. P. Patel, Prof. (Dr.) P. M. George and Prof. (Dr.) V .J .Patel (2014) “Experimental Studies on Perpendicularity of Drilling Operation using DOE”, International Journal of Advance Engineering and Research Development (IJAERD), 1(3), pp. 98–103. Available at: https://ijaerd.org/index.php/IJAERD/article/view/5340 (Accessed: 7 July 2025).