1. The number of inhabited planets in the galaxy;Tang;JBIS,1982
2. The Fermi Paradox: A Forum for Discussion;Martin;JBIS,1979
3. On the improbability of intelligent extraterrestrials;Bond;JBIS,1982
4. On the significance of the apparent absence of extraterrestrials on Earth;Stull;JBIS,1979
5. Constraints limiting the rate of human expansion into the galaxy;Smith;JBIS,1981