1. Stahlke, K.-R., Kraft, K., Kohler, B., Korte, S., Meyer, R.-V., Zirngiebl, E., Reinking, K. & Dziula, H.-J., European Patent Application 326,888 A1 (1989).
2. Wehnert, W., Kohler, K.-H., Reinking, K. & Tresper, E., German Patent Application 3735465 A1 (1989).
3. Kohler, B., Heywang, G. & Zirngiebl, E., German Patent Application 3827644 A1 (1990).
4. Kohler, B., Heywang, G. & Zirngiebl, E., European Patent Application 355,002 A2 (1990).
5. Heinz, H.-D., Schmitt, W., Reinking, K., Kohler, B. & Meyer, R.-V., European Patent Application 381,865 A2 (1990).