Ong , Y. S., N. Yusof, and A. Osmadi. “Challenges of Green Office Implementation: A Case Study in Penang, Malaysia”. International Journal of Sustainable Construction Engineering and Technology, vol. 12, no. 1, May 2021, pp. 153-6, https://publisher.uthm.edu.my/ojs/index.php/IJSCET/article/view/7114.