1. L. Smolin, “The future of spin networks,” gr-qc/9702030.
2. C. Rovelli, Loop quantum gravity, review written for the electronic journal Living Reviews, available as gr-qc/9710008.
3. R. De Pietri, “Canonical “loop” quantum gravity and spin foam models,” gr-qc/9903076.
4. A left-handed simplicial action for Euclidean general relativity
5. Relativistic spin networks and quantum gravity