- 3rd Joint Seminar on Applied Math, Baku State Univ & Zanjan Univ, Baku, Azerbayjan, 2002.
- ICM, Beijing, China (2002), Berlin, Germany (1998), Kyoto, Japan (1990), Berkeley, U. S. A. (1986).
- 26th Aust Conf on Comb Math and Comp, Perth (2001), 23rd Aust Conf on Comb Math and Comp, Brisbane (1998), Australia.
- 44th Annual Meeting, Austral Math Soc, Brisbane, 2000.
- Combinatorics and Graph Theory Workshop, Univ of Queensland, 1999.
- 16th BCC, London (1997), 15th BCC, Univ of Stirling (1995), 15th BCC, Keel Univ (1993), UK.
- 28th AlMC, University of Tabriz (1997), 26th AIMC, (invited speaker), Univ of Kerman (1995), 21st AIMC, Isfahan Univ (1990), 20th AIMC, Tehran Univ (1989), 18th AIMC, (invited speaker), Birjand Univ (1987), 16th AIMC, (invited speaker), Teachers Univ (1985), 15th AIMC, Shiraz Univ (1984).
- University of Calgary, University of Manitoba, University of Toronto, and Simon Frazer University, 1996.
- 8th International Conference on Graph Theory, Combinatorics, Algorithms and Applications, Kalamazoo, Michigan, U. S. A., 1996.
- 26th Annual Conference of Iranian Mathematical Society, invited speaker, University of Kerman, 1995.
- Combinatorial Games Workshop, Mathematical Sciences Research Institute, Berkeley, U. S. A., 1994.
- Univ of Kaiserslautern, Kaiserslautern, Germany, Invited by Professor Dr. Ditmar Schweigert (Math Dep),1993.
- International Conf on: Finite Geometry, Codes and Designs, Shanghai, China, 1993.
- U. S-China Graph Theory Conference, Beijing, June 1993.
- 3rd Islamic Countries Conference on Statistical Sciences (key note speaker), Rabat, Morocco, 1992.
- 2nd International Conf on Combinatorial Mathematics and Computing, Canberra, Australia, 1987.
- National Unive of Singapore, 1992.
- Queensland Univ of Technology, Brisbane, Australia, 1991.
- Univ of Queensland, St. Lucia, Australia, 1991.
- International Colloquium on Words, Languages and Combinatorics (invited), Kyoto, Japan, 1990.
- 2nd Conference on Graph Theory and Combinatorics, Hakone, Japan, 1990.
- Workshop on Group Theory from a Geometrical Viewpoint (invited) Trieste, Italy, 1990.
- 2nd International Catania Combinatorial Conference, Catania, Italy, 1990.
- Graph theory Workshop, University of Otago, New Zealand, 1989.
- Twentieth Annual Conference of Iranian Mathematical Society, Tehran University, 1989.
- Workshop on Block Designs, Institute for Mathematics and Applications, Minnesota, U. S. A., 1988.
- 4th International Conference on Graph Theory, Lanzhu, China, 1987.
- Annual Summer meeting of AMS, University of Oregon, U. S. A., 1984.
- Annual Meeting of AMS, Washington D. C., U. S. A., 1975.
- Univ of Pennsylvania, Combinatorics Seminars, Dep of Math, 1974, 1975.
- Princeton Univ, Dep of Math, 1974.