In Walt Brown's book In the Beginning, a technical note titled Calculations That Show Comets Began Near Earth, references these two papers:
Donald K. Yeomans and Tao Kiang, “The Long-Term Motion of Comet Halley,” Monthly Notices of the Royal Astronomical Society, Vol. 197, 1981, pp. 633–646 at http://adsabs.harvard.edu/abs/1981MNRAS.197..633Y.
Kevin Yau et al., “The Past and Future Motion of Comet P/Swift-Tuttle,” Monthly Notices of the Royal Astronomical Society, Vol. 266, 1994, pp. 305–316 at http://adsabs.harvard.edu/abs/1994MNRAS.266..305Y.
The RSR Research Team may put up an online spreadsheet for calculations based on these comets. We would use Google Docs like we do for bflist.rsr.org.