I. Mathematical Expression:
\(\bullet\) \(-10\leq x_i\leq 10\) , \(i=1,2,3,4\)
 D. Whitley, S. Rana, J. Dzubera, and K. Mathias, "Evaluating Evolutionary Algorithms," Artificial Intelligence, vol. 85, no. 1-2, pp. 245-276, Aug. 1996.
 S. S. Rao, Engineering Optimization: Theory and Practice, 4th ed. Hoboken, New Jersey: John Wiley & Sons, 2009.
 M. M. Ali, C. Khompatraporn, and Z. B. Zabinsky, "A Numerical Evaluation of Several Stochastic Algorithms on Selected Continuous Global Optimization Test Problems," Journal of Global Optimization, vol. 31, no. 4, pp. 635-672, Apr. 2005.
 Ali R. Alroomi, "The Farm of Unconstrained Benchmark Functions," University of Bahrain, Electrical and Electronics Department, Bahrain, Oct. 2013. [Online]. Available: http://www.al-roomi.org/cv/publications