Eduardo C. Guardia and  Jose W. M. Lima and  Afonso H. M. Santos,  A Bathtub Curve from Nonparametric Model.   journal   = {International Journal of Electrical and Computer Engineering}, [online]. World Academy of Science, Engineering and Technology.
    May 2014, vol. 90(6). 877 - 881
    [viewed 22 April 2021]. Available from: https://publications.waset.org/pdf/9998506.