1. Boolos, G.: 1998 ‘Is Hume’s Principle Analytic?’, in Logic, Logic, and Logic, Harvard University Press, Cambridge, MA, pp. 301–314. First published in 1997.
2. Boolos, G.: 1998b, ‘The Standard of Equality of Numbers’, in Logic, Logic, and Logic, Harvard University Press, Cambridge, MA, pp. 202–219. First published in 1990.
3. Boolos, G. and R. Jeffrey: 1990, Computability and Logic, Cambridge University Press.
4. Predicative Logic and Formal Arithmetic