1. ’t Hooft, G.: Probing the small distance structure of canonical quantum gravity using the conformal group. arXiv:1009.0669 [gr-qc]
2. ’t Hooft, G.: The conformal constraint in canonical quantum gravity. arXiv:1011.0061 [gr-qc]
3. ’t Hooft, G.: Quantum gravity without space-time singularities or horizons. In: Erice School of Subnuclear Physics (2009, to be publ.). arXiv:0909.3426
4. DeWitt, B.S.: Theory of radiative corrections for non-abelian gauge fields. Phys. Rev. Lett. 12, 742 (1964)
5. DeWitt, B.S.: Quantum theory of gravity. I. The canonical theory. Phys. Rev. 160, 1113 (1967)