| Ravindra Bapat , Indian Statistical Institute, New Delhi, India, June 24 - July 4, 2012 |
| Mikio Kano , Ibaraki University, , Japan, May 3-11, 2012 |
| Kenta Ozeki , National Institute of Informatics, , Japan, May 3-11, 2012 |
| Alejandro Kocsard , Universidade Federal Fluminense, , Brazil, Jan. 26 - Feb. 19, 2012 |
| Holger Brenner , University of Osnabruck, Osnabruck, Germany, Jan. 4-12, 2012 |
| Reza Naserasr , LRI , Paris, Orsay, France, Dec. 24, 2011 - Jan. 26, 2012 |
| S. M. Bhatwadekar , Tata Institute of Fundamental Research, Mumbai, India, Sep. 1-22, 2006 |
| M. Khalkhali , University of Western Ontario, Ontario, Canada, Aug. 6 - Sep. 3, 2006 |
| Dariush Ehsani , Pennsylvania State University, , USA, July 6 - Aug. 30, 2006 |
| Mahdi Asgari , Oklahoma State University, Stillwater, USA, June 26 - Aug. 3, 2006 |
| Michel Jambu , University of Nice and CIMPA, Nice, France, May 24 - June 2, 2006 |
| Zafar Turakulov , Institute of Nuclear Physics, , Uzbekistan, May 22 - June 12, 2006 |
| Thierry Coulhon , University of Cergy-Pontoise, Cergy-Pontoise , France, May 20-27, 2006 |
| Gilles Carron , University of Nantes, Nantes, France, May 20-26, 2006 |
| Bruno Colbois , University of Neuchâtel, Neuchâtel, Switzerland, May 20-26, 2006 |
| Ahmad El Soufi , University of Tours, Tours, France, May 20 - June 2, 2006 |
| Frank Pacard , University of Paris XII, Paris, France, May 20 - June 1, 2006 |
| Qing Xiang , University of Delaware, Delaware, USA, April 22 - May 1, 2006 |
| Patric Ostergard , Helsinki University of Technology, , Finland, April 22-27, 2006 |
| Jeff Dinitz , University of Vermont, Vermont, USA, April 22 - May 1, 2006 |
| Willem H. Haemers , Tilburg University, Tilburg, The Netherlands, April 21 - May 11, 2006 |
| Aart Blokhuis , Eindhoven University of Technology, Eindhoven, The Netherlands, April 21-30, 2006 |
| Samad Hedayat , University of Illinois at Chicago, Chicago, USA, April 21 - May 4, 2006 |
| Richard Wilson , California Institute of Technology, , USA, April 20 - May 5, 2006 |
| Hadi Kharaghani , University of Lethbridge, Lethbridge, Canada, April 20 - May 20, 2006 |
| Brendan McKay , Australian National University , Canberra, Australia, April 20-30, 2006 |
| Andries E. Brouwer , Eindhoven University of Technology, Eindhoven, The Netherlands, April 9-30, 2006 |
| Elena Konstantinova , Sobolev Institute of Mathematics, Novosibirsk, Russia, April 5 - May 1, 2006 |
| Mariusz Wodzicki , Department of Mathematics, University of California at Berkeley, Berkeley, USA, Sep. 19-25, 2005 |
| Ali Chamseddine , American University of Beirut, Beirut, Lebanon, Sep. 18-24, 2005 |
| Joachim Cuntz , University of Muenster, Muenster, Germany, Sep. 17-23, 2005 |
| Alain Connes , College of France, Paris, France, Sep. 16-24, 2005 |
| Richard Szabo , School of Mathematical and Computer Sciences (MACS), Heriot-Watt University, Edinburgh , Scotland, Sep. 13-20, 2005 |
| Behrang Noohi , Max Planck Institute for Mathematics, Bonn, Germany, Sep. 11-29, 2005 |
| Harald Grosse , Institute for Theoretical Physics, University of Vienna, Vienna, Austria, Sep. 10-15, 2005 |
| Jorge Plazas , Max Planck Institute for Mathematics, Bonn, Germany, Sep. 10-29, 2005 |
| Snigdhayan Mahanta , Max Planck Institute for Mathematics, Bonn, Germany, Sep. 10-23, 2005 |
| Giovanni Landi , Department of Mathematics and Informatics, University of Trieste & SISSA, Trieste, Italy, Sep. 8-16, 2005 |
| Dale Husemoller , Max Planck Institute for Mathematics, Bonn, Germany, Sep. 4-22, 2005 |
| Omran Ahmadi , University of Waterloo, Waterloo, Canada, Aug. 24 - Sep. 3, 2005 |
| Iraj Kalantari , Western Illinois University, Macomb, USA, June 1-30, 2005 |
| Samad Hedayat , University of Illinois , Chicago, USA, May 1-30, 2005 |
| Mostafa Ronaghi , Genome Center, Stanford University, Stanford, USA, April 23, 2005 |
| Vincent Calvez , Ecole Normale Supérieure, Paris, France, April 12-20, 2005 |
| Behshad Behzadi , Ecole Polytechnique, Palaiseau, France, April 11-20, 2005 |
| Dietmar Oelz , Vienna University of Technology, Vienna, Austria, April 10-23, 2005 |
| Peter Markowich , Wolfgang Pauli Institute, Vienna, Austria, April 10-16, 2005 |
| Florian Markowetz , Max Planck Institute for Molecular Genetics, Berlin, Germany , April 9 - May 7, 2005 |
| Reinhard Laue , University of Bayreuth, Bayreuth, Germany, Feb. 15 - March 13, 2005 |
| Wadim Zudilin , Moscow Lomonosov State University , Moscow, Russia, Jan. 17 - Feb. 6, 2005 |
| Marc Rosso , Ecole Normale Superieure, Paris, France, Jan. 15-20, 2005 |
| Barbara Caputo , Royal Institute of Technology (KTH), Stockholm, Sweden, Jan. 6-13, 2005 |
| Ilia Ponomarenko , Steklov Institute of Mathematics, St. Petersburg , Russia , Dec. 29, 2004 |
| Fraydoun Rezakhanlou , University of California, Berkeley, Berkeley, USA, Dec. 25, 2004 - Jan. 20, 2005 |
| Delaram Kahrobaei , University of St Andrews , St Andrews , Scotland, UK, Dec. 21, 2004 - Jan. 6, 2005 |
| Ali Enayat , American University , Washington, USA, Dec. 17, 2004 - Jan. 4, 2005 |
| J. P. Puel , University of Versailles St. Quentin, Versailles, France, Dec. 12-22, 2004 |
| A. El Soufi , University of Tours, Tours, France, Dec. 11-16, 2004 |
| Ph. Kuegler , University of Linz, Linz, Austria, Dec. 9-17, 2004 |
| H. W. Engl , Kepler University of Linz, Linz, Austria, Dec. 9-14, 2004 |
| M. Esteban , University of Paris-Dauphine and CNRS, Paris, France, Dec. 7-22, 2004 |
| R. Popovych , National Academy of Sciences, Kiev, Ukraine, Dec. 6-20, 2004 |
| M. Asadzadeh , Chalmers University of Technology, Göteborg, Sweden, Dec. 5-16, 2004 |
| O. Kavian , University of Versailles St. Quentin, Versailles, France, Dec. 5-24, 2004 |
| U. Saleem , University of the Punjab, Lahore, Pakistan, Dec. 5-17, 2004 |
| H. Shahgholian , Royal Inst. of Technology (KTH), Stockholm, Sweden, Dec. 5-14, 2004 |
| M. Jazar , Lebanese University, Beirut, Lebanon, Dec. 5-17, 2004 |
| F. Murat , Universite Pierre et Marie Curie (Paris VI), Paris, France, Dec. 5-24, 2004 |
| A. Shermenev , Academy of Sciences, Moscow, Russia, Dec. 3-24, 2004 |
| D. Rafiei , Department of Computing Science, University of Alberta, Edmonton, Canada, Sep. 11 - Oct. 21, 2004 |
| K. Salamatian , University of Paris VI, Paris, France, Aug. 14-18, 2004 |
| J. O. Eklundh , Royal Institute of Technology, Stockholm, Sweden, April 26-30, 2004 |
| P. Frosini , Universita di Bologna, Bologna, Italy, April 26-30, 2004 |
| J. P. Thiran , EPFL, Lausanne, Switzerland, April 26-30, 2004 |
| J. M. Geusebroek , University of Amsterdam, Amsterdam, Netherlands, April 26-30, 2004 |
| A. Hero , University of Michigan, Ann Arbor, MI, USA, April 26-30, 2004 |
| P. Cameron , Queen Mary, University of London, London, U.K., April 12 - May 9, 2004 |
| M. Khalkhali , University of Western Ontario, Ontario, Canada, April 3 - May 3, 2004 |
| S. Kabbaj , King Fahd University of Petroleum and Minerals (KFUPM), Dhahran, Saudi Arabia , March 3-12, 2004 |
| Kh. Dehnad , Columbia University, New York, USA, Feb. 23-29, 2004 |
| H. Kharaghani , University of Lethbridge, Lethbridge, Canada, Jan. 28 - Aug. 13, 2004 |
| F. Rezakhanlou , University of California, Berkeley, Berkeley, USA, Dec. 14, 2003 - Jan. 13, 2004 |
| R. Archer , University of Auckland, Department of Engineering Science, Auckland, New Zealand, Dec. 13-18, 2003 |
| Z. (J.) Chen , Southern Methodist University, Department of Mathematics, Texas, USA, Dec. 13-18, 2003 |
| M. Asadzadeh , Chalmers University of Technology, Department of Mathematics, Gِteborg, Sweden, Dec. 13-18, 2003 |
| P. A. Markowich , University of Vienna, Department of Mathematics, Vienna, Austria, Dec. 13-18, 2003 |
| V. Perminov , Kemerovo State University, Belovo, Russia, Dec. 13-18, 2003 |
| N. Emad , University of Versailles, Department of Computer Science , Versailles, France, Dec. 13-18, 2003 |
| A. Iske , Munich University of Technology , Garching, Germany, Dec. 13-18, 2003 |
| Y. Lin , University of Alberta, Department of Mathematical Sciences, Alberta, Edmonton, Dec. 13-18, 2003 |
| A. K. Pani , Indian Institute of Technology Bombay, Department of Mathematics, Mumbai, India, Dec. 13-18, 2003 |
| S. Zhang , Tianjin University, Tianjin, China, Dec. 13-18, 2003 |
| A. Pillay , University of Illinois at Urbana-Champaign, Urbana, USA, Oct. 20-25, 2003 |
| A. Enayat , American University, Washington, USA, Oct. 17-25, 2003 |
| F-V Kuhlmann , University of Saskatchewan , Saskatoon, Canada, Oct. 17-28, 2003 |
| L. van den Dries , University of Illinois at Urbana-Champaign, Urbana-Champaign, USA, Oct. 17-26, 2003 |
| Yuri L. Ershov , Sobolev Institute of Mathematics, Novosibirsk, Russia, Oct. 17-24, 2003 |
| A. Visser , Universiteit Utrecht, , Netherlands, Oct. 17-25, 2003 |
| S. Kuhlmann , University of Saskatchewan, Saskatoon, Canada, Oct. 17-28, 2003 |
| I. Kalantari , Department of Mathematics, Western Illinois University, Macomb, USA, Oct. 11-23, 2003 |
| R. Naserasr , Simon Fraser University, Burnaby, CANADA, Aug. 9-19, 2003 |
| R. Brualdi , University of Wisconsin, Madison, USA, Aug. 9-17, 2003 |
| P. Cameron , Queen Mary, University of London, London, UK, Aug. 8-21, 2003 |
| Ch. Johnson , College of William & Mary, Williamsburg, USA, Aug. 8-17, 2003 |
| C. Thomassen , Technical University of Denmark, Lyngby, Denmark, Aug. 8-18, 2003 |
| W. H. Haemers , Tilburg University, Tilburg, Netherlands, Aug. 7-19, 2003 |
| R. M. Wilson , California Institute of Technology, Pasadena, CA, USA, Aug. 7-17, 2003 |
| H. Kharaghani , University of Lethbridge, Lethbridge, Canada, July 30 - Aug. 31, 2003 |
| S. Shahriari , Pomona College, Claremont, CA, USA, July 28 - Aug. 21, 2003 |
| S. Hedayat , University of Illinois at Chicago, Chicago, USA, July 26 - Aug. 31, 2003 |
| T. Ebrahimi , Signal Processing Laboratory, Swiss Federal Institute of Technology, Lausanne, Switzerland, May 13, 2003 |
| P. Rogaway , Department of Computer Science, University of California, Davis, CA, USA, May 6-15, 2003 |
| L. Shepp , Rutgers University, Piscataway, USA, Feb. 24 - March 1, 2003 |
| F. Natterer , University of Muenster, Muenster, Germany, Feb. 23 - March 1, 2003 |
| R. Cont , Centre de Mathématiques Appliquées, Ecole Polytechnique, Paris, France, Feb. 22 - March 1, 2003 |
| A. Zeghib , Ecole Normale Superieure , Lyon, France, Feb. 8, 2003 |
| H. Shahgholian , Department of Mathematics, Royal Institute of Technology, Stockholm, Sweden, Jan. 7, 2003 |
| F. Rezakhanlou , University of California, Berkeley, Berkeley, USA, Dec. 22, 2002 - Jan. 2, 2003 |
| A. Enayat , American University, Washington, USA, Dec. 19, 2002 - Jan. 7, 2003 |
| S. Hedayat , University of Illinois at Chicago, Chicago, IL, USA, Dec. 8, 2002 - Jan. 8, 2003 |
| B. Mohammadi , Institut Universitaire de France and University of Montpellier, France , Montpellier, France, Nov. 8-15, 2002 |
| A. Plantinga , University of Notre Dame , Indiana, USA, Oct. 20, 2002 |
| Gh. G. Hamedani , Marquette University, Milwaukee, USA, Aug. 19, 2002 - Jan. 15, 2003 |
| A. Miamee , Hampton University, Hampton, USA, June 10 - Sep. 3, 2002 |
| W. Bruns , Universität Osnabrück, Osnabrück, Germany, May 26-30, 2002 |
| H. Holm , Matematisk Institut, Universitetsparken 5, Copenhagen, Denmark, May 23-31, 2002 |
| A. Frankild , Matematisk Institut, Universitetsparken 5, Copenhagen, Denmark, May 23-31, 2002 |
| L. Melkersson , Linkoping University, Linkoping, Sweden, May 23-31, 2002 |
| E. E. Enochs , University of Kentucky, Lexington, USA, May 23-31, 2002 |
| H. B. Foxby , University of Copenhagen - Institute for Mathematical Sciences, Copenhagen, Denmark, May 23-31, 2002 |
| J. Herzog , Universität GH-Essen, Essen, Germany, May 23-31, 2002 |
| L. L. Avramov , University of Nebraska-Lincoln, Lincoln, USA, May 23 - June 5, 2002 |
| I. Swanson , New Mexico State University , Las Cruces, USA, Jan. 6-28, 2002 |
| S. Hedayat , University of Illinois at Chicago, Chicago, USA, Dec. 16, 2001 - Jan. 5, 2002 |
| L. Puel , LRI, Universite de Paris Sud-Orsay, Paris, France, Dec. 9-14, 2001 |
| C. Johnen , LRI, Universite de Paris Sud-Orsay, Paris, France, Dec. 9-14, 2001 |
| M. van Atten , Louvain University, , Belgium, Oct. 22 - Sep. 22, 2001 |
| W. Veldman , Nijmegen University, , Netherland, Oct. 22, 2001 |
| R. Naserasr , Simon Fraser University, Burnaby, CANADA, June 24 - July 11, 2001 |
| H. Movasati , IPM, Tehran, Iran, June 1 - Sep. 26, 2001 |
| J. T. Baldwin , University of Illinois at Chicago, Chicago, USA, May 31 - June 16, 2001 |
| M. Shahshahani , Stanford University, Stanford, USA, Oct. 1, 2000 - July 1, 2001 |
| A. Shekoufandeh , Drexel University, Philadelphia, USA, July 1 - Aug. 1, 2000 |
| H. Kharaghani , University of Lethbridge, Lethbridge, Canada, May 31 - Dec. 31, 2000 |
| M. Shahshahani , Stanford University, Stanford, USA, Feb. 7 - June 9, 2000 |
| M.R. Emamy-K , University of Puerto Rico at Rio Piedras, Rio Piedras, USA, Jan. 15 - May 4, 2000 |
| V. Maillot , ENS, Paris, France, Oct. 29 - Nov. 30, 1999 |
| H. Kharaghani , University of Lethbridge, Lethbridge, Canada, Aug. 9-30, 1999 |
| S. Shahriari , Pomona College, Claremont, CA, USA, June 14 - Aug. 1, 1999 |
| D. Van Dalen , Utrecht University, Utrecht, The Netherlands, May 28 - June 5, 1999 |
| A. Edalat , Imperial College London, London, UK, April 15 - May 15, 1999 |
| E. Mendelsohn , University of Toronto, Toronto, Canada, Nov. 23 - Dec. 23, 1998 |
| W. Ruitenburg , Marquette University, Wisconsin, USA, Oct. 17 - Nov. 11, 1998 |
| A. Edalat , Imperial College London, London, UK, Oct. 15 - Nov. 14, 1998 |
| J.P. Tignol , Universite Catholique de Louvain, , Belgium, Aug. 25 - Sep. 2, 1998 |
| U. Rehman , Universitat Bielefld, Bielefld, Germany, Aug. 25 - Sep. 2, 1998 |
| H. Kiechle , Universitat Munich, Munich, Germany, Aug. 25 - Sep. 2, 1998 |
| A. Barelli , Universite Paul Sabatier, , France, Aug. 16-24, 1998 |
| J. Bellissard , Universite Paul Sabatier, , France, Aug. 16-24, 1998 |
| A. Wassermann , University of Bayreuth, Bayreuth, Germany, Dec. 22, 1997 - Jan. 3, 1998 |
| A. Hilton , Reading University, Whiteknights, UK, Dec. 10-24, 1997 |
| A.E. Zalesskii , University of East Anglia, Nowich, UK, Dec. 10-24, 1997 |
| B. Poizat , Universite Claude Bernard, Villeurbanne, France, Oct. 12 - Nov. 26, 1997 |
| O. Kavian , Universite de Versailles Saint-Quentin-en-Yvelines , Versailles Cedex, France, Aug. 23-26, 1997 |
| S. Zakeri , SUNY at Stony Brook, Stony Brook, USA, July 18 - Sep. 1, 1997 |
| M. Khoshkam , University of Saskatchewan, Saskatchewan, Canada, July 3 - Aug. 3, 1997 |
| M. Shahshahani , Stanford University, Stanford, USA, June 23 - Aug. 11, 1997 |
| Y. Ershov , Novosibirsk State University, Novosibirsk, Russia, June 23 - July 7, 1997 |
| F. Rezakhanlou , University of California, Berkeley, Berkeley, USA, May 28-29, 1997 |
| H. Kharaghani , University of Lethbridge, Lethbridge, Canada, Jan. 9 - Aug. 11, 1997 |
| E.A. Palyutin , Novosibirsk State University, Novosibirsk, Russia, Oct. 1, 1996 - Jan. 1, 1997 |
| R.I. Grigorchuk , Steklov Mathematical Institute, Moscow, Russia, Sep. 1 - Nov. 1, 1996 |
| R.Y. Sharp , University of Sheffield, Sheffield, UK, June 29 - July 8, 1996 |
| M. Brodmann , Institut für Mathematik, Universität Zürich, Zürich, Switzerland, June 29 - July 8, 1996 |
| P. Schenzel , Institut für Informatik Fachbereich Mathematik und Informatik, Martin-Luther, Germany, June 29 - July 8, 1996 |
| M.M. Arslanov , Kazan State University, Kazan, Russia, April 2 - June 6, 1996 |
| G. Jorjadze , Mathematical Institute of the Georgian Academy of Sciences, Tbilisi, Georgia, Oct. 15-21, 1995 |
| A. Sedrakian , Yerevan Physics Institute, Yerevan, Republic of Armenia, Oct. 15-21, 1995 |
| F. Shahidi , Purdue University, West Lafayette, USA, July 1 - Aug. 1, 1995 |
| Francois Murat , Universite Pierre et Marie Curie (Paris VI), Paris, France, June 21, 1995 |
| S. Shahriari , Pomona College, Claremont, CA, USA, Dec. 17, 1994 - Jan. 14, 1995 |
| C.E. Praeger , The University of Western Australia, Nedlands, Australia, Nov. 7-18, 1994 |
| E. Izadi , Harward University, Cambridge, USA, Aug. 17 - Sep. 6, 1994 |
| H. Marandjian , Institute for Informatics and Automation Problems, Yerevan, Republic of Armenia, Aug. 1 - Sep. 1, 1994 |
| H. Shahgholian , Royal Institute of Technology, Stockholm, Sweden, July 2 - Aug. 22, 1994 |
| A.S. Morozov , Novosibirsk State University, Novosibirsk, Russia, July 1 - Oct. 1, 1994 |
| A. Enayat , American University, Washington, USA, June 1 - July 1, 1994 |
| F.R. Drake , Leeds University, Leeds, UK, May 1 - June 1, 1994 |
| D. Anasov , Steklov Mathematical Institute, Moscow, Russia, April 21 - May 5, 1994 |
| H. Kharaghani , University of Lethbridge, Lethbridge, Canada, April 1 - Aug. 1, 1994 |
| S.S. Goncharov , Novosibirsk State University, Novosibirsk, Russia, Jan. 1 - Feb. 1, 1994 |
| A. Enayat , American University, Washington, USA, Jan. 1 - May 1, 1994 |
| A. Enayat , American University, Washington, USA, Jan. 1 - May 1, 1994 |
| A. Morozov , ITEP, Moscow, Russia, Oct. 28 - Nov. 11, 1993 |
| V.G. Kanovei , Moscow State University, Moscow, Russia, Oct. 15, 1993 - Jan. 6, 1994 |
| B. Kalantari , Rutgers University, New Brunswick, USA, Oct. 1, 1993 - July 1, 1994 |
| N.M. Singhi , Tata Institute of Fundamental Research, Bombay, India, Sep. 3-10, 1993 |
| M.R. Emamy-K , University of Puerto Rico at Rio Piedras, Rio Piedras, USA, Aug. 1, 1993 - Feb. 1, 1994 |
| R.I. Grigorchuk , Steklov Mathematical Institute, Moscow, Russia, April 8 - May 14, 1993 |
| C. Lindner , Auburn University, Auburn, USA, March 30 - April 1, 1993 |
| M. Sarrafzadeh , North-Western University, Chicago, USA, Nov. 1 - Dec. 1, 1992 |
| F.H. Bermbach , Johannes-Gutenberg Universitat, Mainz, Germany, Oct. 1, 1992 - May 1, 1993 |
| V. Lyubetski , IPPI, Academy of Science, Moscow, Russia, Sep. 1, 1992 - May 1, 1993 |
| A. Miller , University of Wisconsin-Madison, Madison, USA, Aug. 1 - Sep. 1, 1992 |
| M. Khalkhali , University of Heidelberg, Heidelberg, Germany, Aug. 1-14, 1992 |
| S. Hedayat , University of Illinois at Chicago, Chicago, USA, June 1 - July 1, 1992 |
| B. Kalantari , Rutgers University, New Brunswick, USA, June 1 - July 1, 1992 |
| M. Shahshahani , Stanford University, Stanford, USA, June 1 - Aug. 1, 1992 |
| V.G. Kanovei , Moscow State University, Moscow, Russia, May 1 - June 1, 1992 |
| J.E. Fenstad , University of Oslo, Oslo, Norway, April 1 - May 1, 1992 |
| J. Palis , The Institute for Pure and Applied Mathematics (IMPA), Rio de Janeiro, Brazil, March 1 - April 1, 1992 |
| D. Sullivan , SUNY at Stony Brook, Stony Brook, USA, March 1 - April 1, 1992 |
| J. Larson , University of Florida, Gainesville, USA, Aug. 1 - Sep. 1, 1991 |
| W. Mitchell , University of Florida, Gainesville, USA, Aug. 1 - Sep. 1, 1991 |
| K. Hauser , University of California, Berkeley, Berkeley, USA, Aug. 1 - Sep. 1, 1991 |
| M.A. Shokrollahi , Informatics Institute, Bonn, Germany, Dec. 1, 1990 - Jan. 1, 1991 |
| S. Shokranian , University of Brasilia, Brasilia, Brazil, Dec. 1, 1990 - Jan. 1, 1991 |
| J. Moravscick , Stanford University, Stanford, USA, May 1 - June 1, 1990 |
| D. Kurepa , Belgrade University, Belgrade, Yugoslavia, May 1 - June 1, 1990 |
| D. Follesdal , Institute for Advanced Study, Berlin, Germany, May 1 - June 1, 1990 |
| I. Hacking , University of Toronto, Toronto, Canada, May 1 - June 1, 1990 |
| M. Boffa , Universite de l'Etat a Mons, , Belgium, May 1 - June 1, 1990 |
| R. Chuaqui , University Catholica de Chile, Santiago, Chile, May 1 - June 1, 1990 |
| J. Stern , Ecole Normale Supérieure , Paris, France, May 1 - June 1, 1990 |
| A. Edalat , Imperial College London, London, UK, May 1 - June 1, 1990 |
| A.H. Assadi , University of Wisconsin-Madison, Wisconsin, USA, March 1, 1990 - June 1, 1991 |
| V. Kosygin , Moscow State University, Moscow, Russia, Jan. 1, 1990 |
|