Nicolai, Hermann Quantum Gravity & Unified Theories, AEI-Golm, MPI for Gravitational Physics, Max Planck Society;
206274.pdf (Publisher version), 943KB
Bärwald, O., Gebert, R. W., & Nicolai, H. (1998). On the imaginary simple roots of the Borcherds algebra g II 9,1. Nuclear Physics B, 510(3), 721-738. doi:10.1016/S0550-3213(97)00583-X.