Number Theory, especially Transcendental Number Theory, the Intellectual History of Mathematical Ideas and Mathematics and the Humanities.
- "Mathematics in Twentieth-Century Literature and Art: Content, Form, Meaning," The Johns Hopkins University Press, June 2014.
- "Hilbert's Seventh Problem: Solutions and extensions," (In Press) IMSc Lecture Notes, Chennai, India, 2014.
- Well-approximated points on linear extensions of elliptic curves (with Deanna Caveny), Proceedings of the American Mathematical Society, vol 138, 2010, pages 2745-2754.
- "What is a Number? Mathematical Concepts and Their Origins," The Johns Hopkins University Press, December 2008.
- "Making Transcendence Transparent: An intuitive approach to classical transcendental number theory," (with Edward Burger), Springer, 2004.