G. H. Kaplan and V. V. Makarov (2003), "Astrometric Detection of Binary Companions and Planets: Acceleration of Proper Motion", Astronomische Nachrichten 324, No. 5, pp. 419-424. (Abstract)
The development in Appendix A of the above paper is given in more detail in G. H. Kaplan (2003), "Curved Stellar Paths and Proper Motion Determination", USNO Astronomical Applications Dept. Technical Report No. 2003-02. PostScript PDF
V. V. Makarov and G. H. Kaplan (2005), "Statistical Constraints for Astrometric Binaries with Nonlinear Motion", Astronomical Journal 129, pp. 2420-2427. (Abstract)
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