1. Quantum Gravity (Clarendon Press, Oxford, 2004).
2. and , The nature of Space and Time (Princeton University Press, Princeton, 1996).
3. Inflationary Spacetimes Are Incomplete in Past Directions
4. Reconcile Planck-scale discreteness and the Lorentz-Fitzgerald contraction
5. in: Canonical Gravity: From Classical to Quantum, edited by J. Ehlers and H. Friedrich (Springer, Berlin, 1994).