The Mean Value Theorem in Second Order Arithmetic. - Christopher Hardin; Daniel J. Velleman (J. Symb. Log., 2001)

How the Location of * Influences Complexity in Kleene Algebra with Tests. - Christopher Hardin (LPAR, 2004)

Proof Theory for Kleene Algebra. - Chris Hardin (LICS, 2005)

Modularizing the Elimination of r=0 in Kleene Algebra. - Christopher Hardin (Log. Methods Comput. Sci., 2005)

Agreement in Circular Societies. - Christopher Hardin (Am. Math. Mon., 2010)

On transitive subrelations of binary relations. - Christopher Hardin (J. Symb. Log., 2011)