Jetsada Arnin and  Yodchanan Wongsawat,  On the Verification of Power Nap Associated with Stage 2 Sleep and Its Application.   journal   = {International Journal of Biomedical and Biological Engineering}, [online]. World Academy of Science, Engineering and Technology.
    November 2011, vol. 59(11). 550 - 554
    [viewed 28 January 2020]. Available from: https://publications.waset.org/pdf/1518.