Vasava Kiranbhai Rupsingbhai. “Load Frequency Control of Three Area Power System Using PID Tuning by Ziegler Nichols(Z-N) Method”. International Journal of Advance Research in Engineering, Science & Technology, vol. 3, no. 5, May 2016, pp. 508-11, https://ijarest.org/index.php/ijarest/article/view/663.