Clark R. Chapman (May 2004). "The hazard of near-Earth asteroid impacts on earth". Earth and Planetary Science Letters222 (1): 1–15. doi:10.1016/j.epsl.2004.03.004. Bibcode: 2004E&PSL.222....1C.
Clark R. Chapman (May 2004). "The hazard of near-Earth asteroid impacts on earth". Earth and Planetary Science Letters222 (1): 1–15. doi:10.1016/j.epsl.2004.03.004. Bibcode: 2004E&PSL.222....1C.