We acknowledge gratefully the grants awarded by the Grant Agency of the Czech Republic (No. 205/95/0062) that enabled to collect the optical observations and to work out the global solution used in this study, and by the Grant Agency of the Academy of Sciences of the Czech Republic (No. A3003502) that supported the study of linking the Hipparcos catalog to extragalactic reference frame. Our sincerest thanks belong to the generations of astrometrists (often unknown) all over the world who thoroughly made all the observations used in this study. The help of the IAU, that provided a grant to the Working Group on Earth Rotation in Hipparcos Reference Frame helping thus to convert the data of some observatories into machine-readable form, is also highly appreciated.
© European Southern Observatory (ESO) 1997
Online publication: July 3, 1998