Soner, N. D., B. Chaluvaraju, and B. Janakiram. “The Double Global Domination Number of a Graph”. The Journal of the Indian Mathematical Society 70, no. 1-4 (December 1, 2003): 191–195. Accessed April 30, 2024. https://www.informaticsjournals.com/index.php/jims/article/view/21949.