Hashem-Nazari, Mohammad, et al. “Non-Equidistant ‘Basic Form’-Focused Grey Verhulst Models (NBFGVMs) for Ill-Structured Socio-Economic Forecasting Problems”. Journal of Business Economics and Management, vol. 18, no. 4, Aug. 2017, pp. 676-94, https://doi.org/10.3846/16111699.2017.1337045.