**Recursion Theory of Ramsey's Theorem: Universita degli Studi di Siena, April 2006:**
Lecture 1
Lecture 2
Lecture 3
Lecture 4
Lecture 5
Lecture 6

Logic Colloquium, University of California, Berkeley, November 18, 2005:

AMS meeting (in honor of retirement of Manuel Leman), Storrs, October 28-29, 2006:

CIE 2007, Siena, June 19, 2007:

American Mathematical Society-New Zealand Mathematical Society Joint Meeting, December 2007:

Reverse Mathematics: Foundations and Applications, Chicago, December 2009:

Conference on Computability Theory and Randomness, Nanjing, June 2008: