“…On other hand for x s ∈ V (Γ) V (Γ χ ) we have that χ(x s ) = 0 and there is a vertex v i, j ∈ V (Γ χ ) such that there is an edge between x s and v i, j . Then [v i, j , x s ] = 0, hence by (6) [λ i, j x 1 + ∑ 2≤t≤ j λ i, j,t y i,t , x s ] = 0. Then (8) [x 1 , x s ] ∈ {y i,t , x s } i,t,s .…”