Kulikova, O.V.
(Algebra and Discrete Mathematics, 2004)
The paper is a generalization of [2]. For a group
H = ‹A|O›, conditions for the equality Ñ₁ ∩ Ñ₂ = Ñ₁, Ñ₂] are
given in terms of pictures, where Ñi is the normal closure of a set R¯
i ⊂ H for i = 1, 2.