Starchak, M.R. 2021. A proof of Bel’tyukov-Lipshitz theorem by quasi-quantifier elimination. I. Definitions and GCD-lemma. Vestnik of Saint Petersburg University. Mathematics. Mechanics. Astronomy. 8, 3 (Sep. 2021), 455–466. DOI:https://doi.org/10.21638/spbu01.2021.307.