1. NASA laid the foundation for formal and coordinated studies of the artificial debris environment at the NASA Orbital Debris Workshop,1982
2. XXV COSPAR Conference,1984
3. XXVI COSPAR Conference, June 1986 and at the IAA Symposium on Space Safety and Rescue,1986
4. History and consequences of on-orbit breakups;Johnson;Advances in Space Research,1985
5. History of On-Orbit Satellite Fragmentations;Johnson,1986