Blair, S. K.; Magnani, L.; Brand, J.; Wouterloot, J. G. A. (2008). "Formaldehyde in the Far Outer Galaxy: Constraining the Outer Boundary of the Galactic Habitable Zone". Astrobiology. 8 (1): 59–73. Bibcode:2008AsBio...8...59B. doi:10.1089/ast.2007.0171. PMID18266563.
Blair, S. K.; Magnani, L.; Brand, J.; Wouterloot, J. G. A. (2008). "Formaldehyde in the Far Outer Galaxy: Constraining the Outer Boundary of the Galactic Habitable Zone". Astrobiology. 8 (1): 59–73. Bibcode:2008AsBio...8...59B. doi:10.1089/ast.2007.0171. PMID18266563.
Mullen, Leslie (May 18, 2001). "Galactic Habitable Zones". NAI Features Archive. Nasa Astrobiology Institute. Archived from the original on April 9, 2013. Retrieved May 9, 2013.
Blair, S. K.; Magnani, L.; Brand, J.; Wouterloot, J. G. A. (2008). "Formaldehyde in the Far Outer Galaxy: Constraining the Outer Boundary of the Galactic Habitable Zone". Astrobiology. 8 (1): 59–73. Bibcode:2008AsBio...8...59B. doi:10.1089/ast.2007.0171. PMID18266563.
Mullen, Leslie (May 18, 2001). "Galactic Habitable Zones". NAI Features Archive. Nasa Astrobiology Institute. Archived from the original on April 9, 2013. Retrieved May 9, 2013.