00540naa#a2200169#i#450# EN\\bibl\43484 20211203202853.5 2072-9502 20210415b2021####ek#y0engy0150####ca RU PRINCIPLES OF FORMAL CLASSIFICATION THEORY OF TECHNICAL SYSTEMS: CASE OF ENERGY FACILITIES Article Astrakhan Astrakhan State Technical University 2021 12 с. Article local Математика. 51 Fedorova Natalia Vasilyevna vestnik.astu.org