On consecutive factors of the lower central series of right-angled Coxeter groups

We study the lower central series of a right-angled Coxeter group $RC_{\mathcal K}$ and the corresponding associated graded Lie algebra $L(RC_{\mathcal K})$ and describe the basis of the fourth graded component of $L(RC_{\mathcal K})$ for any ${\mathcal K}$.