Halbgruppen und Automaten Willibald Dörfler (1973) Rendiconti del Seminario Matematico della Università di Padova
Hiérarchies de concaténation Jean-Eric Pin (1984) RAIRO - Theoretical Informatics and Applications - Informatique Théorique et Applications
Homomorphic correspondences of relational systems František Krutský (1983) Acta Universitatis Palackianae Olomucensis. Facultas Rerum Naturalium. Mathematica
Hotz-isomorphism theorems in formal language theory Volker Diekert, Axel Möbus (1989) RAIRO - Theoretical Informatics and Applications - Informatique Théorique et Applications
How much semigroup structure is needed to encode graphs ? P. Goralčík, A. Goralčíková, V. Koubek (1986) RAIRO - Theoretical Informatics and Applications - Informatique Théorique et Applications