  This work aims to explore the possibilities of determining the long-period
part of the precession-nutation of the Earth with techniques other than very
long baseline interferometry (VLBI). Lunar laser ranging (LLR) is chosen for
its relatively high accuracy and long period. Results of previous studies could
be updated using the latest data with generally higher quality, which would
also add ten years to the total time span. Historical optical data are also
analyzed for their rather long time-coverage to determine whether it is
possible to improve the current Earth precession-nutation model.
