of Asteroid Families", in Asteroids III, pp. 633–643, University of Arizona Press (2002), Hirayama, Kiyotsugu; "Groups of asteroids probably of common origin", Astronomical Journal, Vol. 31, No. 743, pp. 185-188 (October 1918). Nesvorný, David; Bottke Jr., William F.; Dones, Luke; and Levison, Harold F.; "The recent breakup of an asteroid in the main-belt region", Nature, Vol. 417, pp. 720-722 (June 2002). Zappalà, Vincenzo; Cellino, Alberto; Farinella, Paolo; and Knežević, Zoran; "Asteroid families I - Identification by hierarchical clustering and reliability assessment", Astronomical Journal, Vol. 100, p. 2030 (December 1990). Zappalà, Vincenzo; Cellino, Alberto; Farinella, Paolo; and Milani, Andrea; "Asteroid families II - Extension to unnumbered multiopposition asteroids", Astronomical Journal, Vol. 107, pp. 772-801 (February 1994) M. S. Kelley & M. J. Gaffey 9 Metis and 113 Amalthea: A Genetic Asteroid Pair, Icarus Vol. 144, p. 27 (2000). External links Planetary Data System - Asteroid Families dataset, as per the Zappalà 1995 analysis. Latest calculations of proper elements for numbered minor planets at astDys. Asteroid (and Comet) Groups by Petr Scheirich (with excellent plots). Asteroid Families Portal Families