1. Gehrels, T., editor, "Physical Studies of Minor Planets, 'I NASA SP-267, 1971.
2. Roberts, D. L. "Proceedings of the Cometary Science Working Group, 'I IIT Resea.rch Institute Publication, 1971.
3. "A Mission Analysis Study of Comet Rendezvous and Asteroid Docking" JPL Report 760-71. (JPL Internal Document) 15June 1972.