Vorob’ev, N. N., and A. A. Tsarev. “On the Modularity of a Lattice of $τ$-Closed $n$-Ultiply $ω$-Composite Formations”. Ukrains’kyi Matematychnyi Zhurnal 62, no. 4 (April 25, 2010): 453–463. Accessed April 20, 2024. https://umj.imath.kiev.ua/index.php/umj/article/view/2879.