Thanrak, Chotitham, and Sasalak Tongkaw. “Mathematical Model for Approximation the Efficiency of Parallel Computing on Single Board Cluster With Least-Squares Approximation”. International Journal of Integrated Engineering, vol. 12, no. 7, Oct. 2020, pp. 181-6, https://publisher.uthm.edu.my/ojs/index.php/ijie/article/view/7269.