  The recent radial velocity Keck data for GJ876 in Laughlin et al. (2005) is
shown to be in good agreement, apart from a 6 m/s scatter, with a theoretical
calculation (Nauenberg, 2002) based on orbital parameters from a fit to the
earlier Keck data. The time variation of the periods of the inner and outer
planets, which are locked in a near 2:1 resonance, are evaluated, and their
mean values, Pi and Po, are shown to satisfy closely the relation Po/Pi=2+Po/P,
where P is the period for the retrograde precesion of the common mean
periastron of these planets.
