Joint Mathematics Meetings, San Diego, January 2008.
MathFest, San Jose, August, 2007.
Joint Mathematics Meetings, New Orleans, January, 2007.
MathFest, Knoxville, August, 2006.
Joint Mathematics Meetings, San Antonio, January, 2006.
MathFest, Albuquerque, August, 2005.
Joint Mathematics Meetings, Atlanta, January, 2005.
MathFest, Providence, August, 2004.
Joint Mathematics Meetings, Phoenix, January, 2004.Joint Mathematics Meetings, Baltimore, January, 2003.
Joint Mathematics Meetings, San Diego, January, 2002.
Joint Mathematics Meetings, New Orleans, January, 2001.