Ε. Giovanis,  Proposal of Additional Fuzzy Membership Functions in Smoothing Transition Autoregressive Models.   journal   = {International Journal of Economics and Management Engineering}, [online]. World Academy of Science, Engineering and Technology.
    April 2010, vol. 40(4). 453 - 457
    [viewed 07 May 2021]. Available from: https://publications.waset.org/pdf/9865.