1. M.B. Green and J.H. Schwarz, CalTech preprints CALT-68-1182, 1194;
2. E. Witten, Princeton preprints;
3. P. Candelas, G.T. Horowitz, A. Strominger and E. Witten, Santa Barbara preprint NSF-1TP-84-170;
4. Heterotic String
5. An analogue model for KSV theory