Yegorova-Gudkova, T., Bojko, M., Neustroiev, Y., Khostash, O., Pan, L., Shepitko, H., Beloborodko, V., Zvirkov, O., Kirilina, M., & Matjukhina, I. (2021). Development of an innovative methodology of research of systems on an example of a shadow economy as an invariant of system of economic security of state. Technology Audit and Production Reserves, 4(4(60), 41–45. https://doi.org/10.15587/2706-5448.2021.239035