Gusev V S., Vernikov B.M., “Chain Varieties of Monoids”, Diss. Math., 2018, no. 534, 1–73
O. Sapir, “The finite basis problem for words with at most two non-linear variables”, Semigr. Forum, 93:1 (2016), 131–151
Sapir O., “Finitely Based Monoids”, Semigr. Forum, 90:3 (2015), 587–614
J. Math. Sci. (N. Y.), 209:4 (2015), 588–599
Lee E.W.H., “on Certain Cross Varieties of Aperiodic Monoids With Commuting Idempotents”, Results Math., 66:3-4 (2014), 491–510