Second Workshop on Differential Algebra and Related Topics, Rutgers University at Newark, April 12-13, 2007.

Arizona Winter School on Fundamental groups in arithmetic, Albuquerque, New Mexico, March 12-16, 2005.

Groupes de Galois Arithmetiques et differentiels, CIRM, Luminy, France, March 8-13, 2004.

Logic and Number Theory, Arizona Winter School, Tucson, Arizona, March 15-19, 2003.

Solving Systems of Polynomial Equations, CBMS Lectures Series by Bernd Sturmfels, Texas A&M University, College Station, Texas, May 20-24, 2002.

AMS Annual Meeting, Marriott & Sheraton Hotels, New Orleans, January 10-13, 2001. (Participation sponsored by MSRI).

Workshop on Differential Algebra and Related Topics, Rutgers University at Newark, November 2-3, 2000. (Participation sponsored by organizers).

Mathematical Challenges of the 21st Century, University of California at Los Angeles, August 7-12, 2000. (Participation sponsored by AMS travel grant).

Aspects of Algebraic Geometry and Commutative Algebra, Texas A&M University, May 18-20, 2000. (Participation sponsored by the organizers.)

Groupes de Galois Differentiels, CIRM, Luminy, France, February 22-26, 1999. (Participation sponsored by the organizers and The University of Oklahoma Graduate College.)

Trends in the Representation Theory of Finite Dimensional Algebras, Joint Summer Research Coference of the American Mathematical Society, University of Washington at Seattle, July 20-24, 1997. (Participation sponsored by the organizers and the University of Oklahoma Graduate College.)

XXVI National Congress of the Mexican Mathematical Society, Morelia, Mexico, October 10-16, 1993. (Participation sponsored by the UNAM.)