Yegorova-Gudkova, T.; Bojko, M.; Neustroiev, Y.; Khostash, O.; Pan, L.; Shepitko, H.; Beloborodko, V.; Zvirkov, O.; Kirilina, M.; Matjukhina, I. 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. TAPR 2021, 4, 41-45.