There are three principal sources of radial velocity data used
in the present compilation: the General Catalogue of Stellar Radial
Velocities (Wilson 1953) and the catalogue of Evans (1978), both
accessed via the SIMBAD data base, and the catalogue of Barbier-Brossat
(1989) which was later included in the INCA data base. The
correspondence between the letters used in this field and the source of
the data, along with the number of stars whose radial velocity was
taken from this source, is given in Table B4 
.
[]
The data given here are very incomplete as they do not
include most radial velocities obtained by cross-correlation methods
(not yet published or published in small lists). Furthermore, they do
not include the results of the ongoing observations organised in
parallel with the work of preparation of the Hipparcos Input Catalogue.
In the northern hemisphere, a radial velocity programme for early-type
stars brighter than 
mag
has been in progress since mid-1982 using objective-prism techniques
and a slit spectrograph (Fehrenbach & Burnage 1985; Grenier 1988;
Burnage et al. 1988). In the southern hemisphere, three ESO
key-programmes have been in progress since the end of 1988, two for
early-type stars (one for stars nearer than 100pc, one for stars in OB
and early-A associations), and one for late-type stars using the
Coravel spectrometer (one measurement has already been obtained for
each of the 20000 or so stars on the observing
programme). These three programmes are described by Gerbaldi et al.
(1990), Hensberge et al. (1990), and Mayor et al. (1990).
