00603naa#a2200169#i#450# EN\\bibl\38190 20240429150627.1 2686-9896 20200616b2020####ek#y0engy0150####ca RU ABOUT EXISTENCE MODEL COMPANION Journal article Angarsk Federal State Funded Educational Establishment of Higher Education «Angarsk State Technical University» 2020 0 с. Journal article local Общие вопросы математики. 27.01 grnti Chihachev Sergey Aleksandrovich angtu.editorum.ru