Apté, C., Damerau, F., & Weiss, S. M. (1994). Towards language independent automated learning of text categorization models. Proceedings of the 17th Annual International ACM SIGIR Conference on Research and Development in Information Retrieval (pp. 23–30). Biebricher, P., Fuhr, N., Lustig, G., Schwantner, M., & Knorz, G. (1988). The automatic indexing system AIR/PHYS—from research to application.