[1] S. Bogdanović: Semigroups with a system of subsemigroups. Inst. of Math., Novi Sad, 1985. MR 0812051

[2] S. Bogdanović and M. Ćirić: Semigroups. Prosveta, Niš, 1993 (Serbian).

[3] S. Bogdanović and M. Ćirić: Semilattices of Archimedean semigroups and (completely) $\pi $-regular semigroups, I. Filomat (Niš) 7 (1993), 1–40 (Survey Article). MR 1301859

[4] M. Ćirić and S. Bogdanović: Decompositions of semigroups induced by identities. Semigroup Forum 46 (1993), 329–346. DOI 10.1007/BF02573576 | MR 1206211

[5] M. Ćirić and S. Bogdanović: Semilattice decompositions of semigroup. Semigroup Forum 52 (1996), 119–132. DOI 10.1007/BF02574089 | MR 1371796

[6] A. H. Clifford and G. B. Preston: The algebraic theory of semigroups. Vol 1, Amer. Math. Soc., 1961. MR 0132791

[7] D. W. Miller: Some aspects of Green’s relations on periodic semigroups. Czechoslovak Math. J. 33 (108) (1983), 537–544. MR 0721084 | Zbl 0538.20030

[8] M. Petrich: Lectures in semigroups. Akad. Verlag, Berlin, 1977. MR 0447437 | Zbl 0369.20036

[9] M. Petrich: Semigroup certain of whose subsemigroups have identities. Czechoslovak Math. J. 16 (91) (1966), 186–198. MR 0200370

[10] B. Ponděliček: A certain equivalence on a semigroup. Czechoslovak Math. J. 21 (95) (1971), 109–117. MR 0283110

[11] M. S. Putcha: Semigroups in which a power of each element lies in a subgroup. Semigroup Forum 5 (1973), 354–361. MR 0316613 | Zbl 0259.20052

[12] M. S. Putcha: Semilattice decompositions of semigroups. Semigroup Forum 6 (1973), 12–34. DOI 10.1007/BF02389104 | MR 0369582 | Zbl 0256.20074

[13] J. T. Sedlock: Green’s relations on a periodic semigroup. Czechoslovak Math. J. 19 (94) (1969), 318–322. MR 0244426 | Zbl 0214.03504

[14] L. N. Shevrin: Theory of epigroups I. Mat. Sbornik 185 (1994), no. 8, 129–160. (Russian) MR 1302627 | Zbl 0839.20073

[15] T. Tamura: On Putcha’s theorem concerning semilattice of Archimedean semigroups. Semigroup Forum 4 (1972), 83–86. DOI 10.1007/BF02570773 | MR 0297663 | Zbl 0256.20075