Mount Allison University, Sackville, NB, Canada; 8--12 June 1998.

Workshop, Fields Institute, Toronto, Canada; 23--28 September 2002.

McGill University, Montreal, Canada; 16--17 October 1999.

Categorical Methods in Algebra and Topology - Commemorating 25 years of Category Theory in Bremen. University of Bremen, Germany; 21--25 August 2000.

Villa Olmo, Como, Italy; 16--22 July 2000.

Canadian Mathematical Society Annual Seminar. Dalhousie University, Halifax, Canada; 9--15 July 1995.

University of Coimbra, Portugal; 19--24 July 1999.

Category Theory and Computer Science. University of Ottawa, Ontario, Canada; 15--17 August 2002.

7th conference on Category Theory and Computer Science. S. Margherita Ligure, Italy; 4--6 September 1997.

8th conference on Category Theory and Computer Science. Edinburgh, Scotland, UK; 10--12 September 1999.

ICMS, Edinburgh, Scotland, UK; 2--7 June 2003.

Peripatetic Seminar on Sheaves and Logic. UCL, Louvain-la-Neuve, Belgium; 16--17 October 1999.

University of Coimbra, Portugal; 13--17 July 1999.