E. A. Tkachenko and  E. M. Rogova and  V. V. Klimov,  Evolution of Performance Measurement Methods in Conditions of Uncertainty: The Implementation of Fuzzy Sets in Performance Measurement.   journal   = {International Journal of Economics and Management Engineering}, [online]. World Academy of Science, Engineering and Technology.
    September 2016, vol. 112(4). 1381 - 1388
    [viewed 05 August 2020]. Available from: https://publications.waset.org/pdf/10005751.