Nicolai, H. Quantum Gravity & Unified Theories, AEI-Golm, MPI for Gravitational Physics, Max Planck Society;
Nicolai_1987.pdf (beliebiger Volltext), 2MB
Nicolai, H. (1987). What are string theories? Progress in Particle and Nuclear Physics, 19, 1-31. doi:10.1016/0146-6410(87)90002-0.