WASET
    Hairulliza M. Judi and  Soon Y. Chee,  Visualising Energy Efficiency Landscape.   journal   = {International Journal of Mathematical and Computational Sciences}, [online]. World Academy of Science, Engineering and Technology.
    May 2009, vol. 29(5). 309 - 312
    [viewed 29 March 2024]. Available from: https://publications.waset.org/pdf/599.