Cosmic Ancestry: The Modern Version of Panspermia - The Cosmic Ancestry hypothesis - about which this site has a large amount of information - treats all of evolution, not just the origin of life on Earth, as due to interaction with cosmic microorganisms.
Panspermia - Descriptive entry in The Encyclopedia of Astrobiology, Astronomy, and Spaceflight.
Panspermia Revisited - Short scientific article by John R. Gribbin. "Spreading of life-bearing spores across the Galaxy (panspermia) may be easier than is usually acknowledged."
