Klochko, E. N., D. Nasimov, R. V. Gurfova, and T. Y. Tokareva. “The Essence of the Conceptual Model of Service Enterprises Modernization”. International Journal of Economics and Financial Issues, vol. 6, no. 1S, May 2016, pp. 187-94, https://www.econjournals.com/index.php/ijefi/article/view/2377.