Original text in Italian can be found here.

**Graph Theory in Sicily **

*by Mario Gionfriddo*

Graph Theory and Block-Designs Theory in Sicily have very precise dates of origin. Graph Theory in Sicily started in 1969 with some seminars given by F. Speranza, Full Professor of Differential Geometry at University of Messina. F. Speranza continued his studies in Differential Geometry and Graph Theory, later devoting his attention to Mathematics Education and Mathematical Logics.

At that time the graphs were called *singrams*, and that was the name used for graphs in some of Speranza’s research papers. A few years later, it was Speranza who pushed me to study Graph Theory.

Block-Designs Theory in Sicily began in May 1978 with seminars hosted by C.C. Lindner at University of Messina. Furthermore, we can precisely say that the first paper in Sicily on Steiner Systems is [M. Gionfriddo, C.C. Lindner, Construction of Steiner quadruple systems having a prescribed number of blocks in common, Discrete Mathematics 34 (1981), p. 31-42]. Lindner came to Messina as Visiting Professor covered by a grant of INdAM-GNSAGA.

So, a long scientific cooperation had started which still continues today. After myself, many other researchers from Messina and Catania of Designs Theory have cooperated with him and they have established strong scientific cooperations, that are alive even today.

In 1981, I moved to Catania after being offered a Full Professorship position at the University of Catania. Therefore, we can say that 1981 was the year that Graph Theory and Design Theory were introduced to Catania. In 1986 I organized the Congress “1st International Catania Combinatorial Conference: Graphs, Steiner Systems and their applications” held in Santa Tecla, September 12-17, 1986. Many well-known scholars of graph theory and hypergraphs attended this congress, among them, C. Berge, F. Harary, C. Thomassen, S. Simic, S. Fiorini, G. Sabidussi, Zs. Tuza. As well as recognized researchers of Design Theory, such as C. Coulbourn, C.C. Lindner, A. Rosa, C. Rodger, L. Teirlink, K. Phelps.

The second congress followed three years later, as the “2nd International Catania Combinatorial Conference: Graphs, Designs and Combinatorial Goemetries”, Santa Tecla, September 3-9, 1989, with the notable presence of Paul Erdos, surely one of the greatest mathematicians of the XX century.

The third congress took place in 1992. On that occasion, the congress became part of the International Congress Series “Combinatorics”, which has been organized in Italy every two years till today: “3rd International Catania Combinatorial Conference: Combinatorics 1992”, Santa Tecla, September 12-17, 1992”. In that event, the number of participants exceeded 250, including once again among others Paul Erdos.

After that congress a long series of yearly workshops stepwise organized in Catania, Messina and also Malta with J. Lauri. At the same time, since 1993, V. Voloshin from University of Kinishev in Moldavia had started to visit the Departments of Mathematics in Catania and Messina: the scientific achievements obtained thanks to him are numerous, relevant and of great quality. A scientific cooperation that even today is of current relevance. Vitaly Voloshin is today Full Professor at Troy University in Alabama (USA).

In 2004 another international congress of the “Combinatorics” series took place, with the usual unavoidable success in terms of participants and communications of great level: “4th International Catania Combinatorial Conference: Combinatorics 2004”, Capomulini, September 12-17, 2004.

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