In accordance with the mathematical definition of sustainability, the trajectory is called sustainable if for arbitrarily small limiting deviation determining the sustainability corridor one can indicate such restrictions for perturbations under which the system does not leave this corridor (Bobylev et al., 2015). In other words, speaking of sustainability, it is necessary to determine-the invariance of which properties of the economic system are significant and to what extent. Moreover, it is necessary to characterize the perturbation, concerning which the economic system will be sustainable. Obviously, more the significant of the external impact, less is the system is able to maintain the original parameters. Therefore, in the scientific literature, new methods of assessing the sustainability of economic systems are investigated both in general (Chechushkov et al., 2018) and in certain spheres and sectors (Chernikova et al., 2018; Ciambriello & Dimitri, 2015; Strielkowski & Astachova, 2017).
Theoretical and Methodological Approaches to the Problems of Control of the Economic Systems Sustainability
The sustainability of the economic systems can be considered at different levels of the economic relations. At the macro level, the sustainability issues are directly related to ensuring the macroeconomic equilibrium, with two main types of sustainability-the adaptive sustainability and the sustainability of substitution. The first type is based on the mechanism of compensation of the internal or external disturbing influences, while the second one implies the possibility for the economic system to evade completely the effect of the disturbing factors and not to have appropriate compensatory mechanisms. The sustainability at the meso-level is determined by the viability of the system, taking into account the specifics of this region. Economic sustainability at the micro level is manifested in the sustainability of the functioning parameters of certain economic agents. For example, a fundamental condition for the successful operation of any enterprise is the provision of a sustainable financial state (Abrashkin et al., 2017).
In terms of this article, taking into account the importance of the managerial aspect, it seems expedient to pay special attention to the existing theoretical and methodological approaches that reveal the mechanisms for ensuring the sustainability of the economic systems. The development of this problem is closely connected with the evolution of the methodological directions of the system approach.
One of the first issues of sustainability in the context of a systemic worldview was explored in the early twentieth by Bogdanov in the course of development of the tectology "General Organizational Science'" (Bogdanov, 1989). In this regard, the conclusion that the sustainability of the equilibrium of all organizational forms is determined by the sustainability of the weakest link is extremely relevant for the modern times as well. The modern system of banking regulation and supervision is essentially based on this thesis-the timely removal of financially unsustainable credit institutions from the market is the key to the sustainable functioning of the banking system as a whole.
The significant stage in the development of the system approach is the scientific papers of Bertalanffy, who is considered to be a founder of the general theory of systems (Bertalanffy, 1969).
Further development of the system approach and the understanding of the regularities of ensuring the system's sustainability are associated with cybernetics and homeostatic. Being a science studying the control systems, cybernetics in matters of sustainable development focuses on direct and reverse communications. If the direct communication is the direct influence of the control subject on the object, then the feedback is the response of the object to the managerial impact (Wiener, 1958). Note that the special attention is paid to the concept of...