1. Performance of Earth-to-Orbit Transports Breathing Air;Dorrington,1989
2. The National Aero-Space Plane Program;Barthelemy,1989
3. SAENGER The German Aerospace Vehicle Program;Hoegenauer,1989
4. SAENGER Space Transportation System Progress Report 1989;Koelle,1989
5. A Future Launcher for Europe;Conchie,1989