Nakamura, T.; Kurahashi, H. Veljača 1998. Collisional Probability of Periodic Comets with the Terrestrial Planets an Invalid Case of Analytic Formulation. Astronomical Journal. 115 (2): 848. Bibcode:1998AJ....115..848N. doi:10.1086/300206
Nakamura, T.; Kurahashi, H. Veljača 1998. Collisional Probability of Periodic Comets with the Terrestrial Planets an Invalid Case of Analytic Formulation. Astronomical Journal. 115 (2): 848. Bibcode:1998AJ....115..848N. doi:10.1086/300206
Images of Chicxulub Crater. NASA/JPL Near-Earth Object Program Office. 22. kolovoza 2005. Inačica izvorne stranice arhivirana 28. veljače 2013. Pristupljeno 15. veljače 2013.
Images of Chicxulub Crater. NASA/JPL Near-Earth Object Program Office. 22. kolovoza 2005. Inačica izvorne stranice arhivirana 28. veljače 2013. Pristupljeno 15. veljače 2013.