Impact of Comet Shoemaker-Levy 9-Size, Origin, and Plumes: Comparison of Numeri 9.95 Academic Press 1997 paperback 245319 1 a y 2 pp. 317- 330 2 y Roulston, Mark S.; Thomas J. Ahrens Impact Mechanics and Frequency of SL9-Type Events on Jupiter," REPRINT