classic papers of the week -- 18

Atlas of Peculiar Galaxies

• Arp, Halton

Thresholds for Creation of Particles

• Feshbach, H. (Massachusetts Institute of Technology, Cambridge, Massachusetts), Schiff, L. I. (University of Pennsylvania, Philadelphia, Pennsylvania)

Particles, environments, and possible ecologies in the Jovian atmosphere

• Sagan, C., Salpeter, E. E. (Cornell University, Ithaca, N.Y.)