Cильно бескубные слова и свободная бернсайдова полугруппа с тождеством $x^2=x^3$ и двумя образующими

In this paper we consider the free Burnside semigroup with two generators satisfying $x^2=x^3$. Elements of this semigroup are classes of equivalent words. We prove that each such equivalence class contains at most one overlap-free word.