M. V. Volkov, S. V. Goldberg, S. I. Kublanovsky, “A minimal infinitely based semigroup whose variety is polynomially recognizable”, Fundam. Prikl. Mat., 16:3 (2010), 105–122; J. Math. Sci., 177:6 (2011), 847–859
J. Almeida, M. V. Volkov, S. V. Gol'dberg, “Complexity of the identity checking problem for finite semigroups”, Zap. Nauchn. Sem. POMI, 358 (2008), 5–22; J. Math. Sci. (N. Y.), 158:5 (2009), 605–614