1. O. Anderson,Ein Bericht uber Structur abstrakter Halbgruppen, Thesis, Hamburg, 1952.
2. S. Bogdanović,Semigroups of Galbiati-Veronesi, Proc. of the Conf. “Algebra and Logic”, Zagreb, (1984), 9–20, Novi Sad 1985.
3. S. Bogdanović,Semigroups with a system of subsemigroups, Inst. of Math. Novi Sad, 1985.
4. S. Bogdanović and M. Ćirić,Semigroups in which the radical of every ideal is a subsemigroup, Zbornik radova Fil. fak. Niš,6 (1992), 129–135.
5. S. Bogdanović and M. Ćirić,Chains of Archimedean semigroups (Semiprimary semigroups), Indian J. Pure Appl. Math. (to appear).