Safiullin, Marat Rashitovich, et al. “Methodological Approaches to the Diagnosis and Forecast of the Long-Wave Fluctuations in the Economy”. International Journal of Economics and Financial Issues, vol. 6, no. 4, Oct. 2016, pp. 1616-24, https://mail.econjournals.com/index.php/ijefi/article/view/3028.