WASET
    Zhang Yan and  Yu Bin,  Non-negative Principal Component Analysis for Face Recognition.   journal   = {International Journal of Electronics and Communication Engineering}, [online]. World Academy of Science, Engineering and Technology.
    December 2010, vol. 48(12). 1794 - 1798
    [viewed 23 April 2024]. Available from: https://publications.waset.org/pdf/14158.