S. A. Grigoryan, V. H. Tepoyan, “On isometric representations of the perforated semigroup”, Lobachevskii Journal of Mathematics, 34:1 (2013), 10.1134/S1995080213010046 , 4 pp., arXiv: https://arxiv.org/abs/1303.0387
T. A. Grigoryan, E. V. Lipacheva, V. H. Tepoyan, “On $\pi$-extensions of the semigroup $\mathbb{Z}_+$”, Uch. zapiski EGU, ser. Fizika i Matematika, 2013, no. 1, 3–5
2012
5.
T. A. Grigoryan, E. V. Lipacheva, V. A. Tepoyan, “On the extension of the Toeplitz algebra”, Physics and mathematics, Kazan. Gos. Univ. Uchen. Zap. Ser. Fiz.-Mat. Nauki, 154, no. 4, Kazan University, Kazan, 2012, 130–138