The extragalactic database was used by Garcia (Garcia et al. 1993;
Garcia 1993)
for a general study of group membership of all galaxies with a radial
velocity less or equal to 5500 
and an apparent magnitude brighter
than bt=14. Two automatic algorithms were used simultaneously
(percolation and hierarchy clustering methods) for
producing very robust groups. From the whole sample 485 groups were build.
They are identified by the acronym LGG (for Lyons Galaxy Group).
For a galaxy, the LGG number lgg gives the group to which the galaxy belongs.
The lgg number is available for 2702 galaxies.
Acknowledgements
We are grateful to those who contributed to LEDA extragalactic database: Becker M., Bravo H., Buta R.J., Corwin H.G., Davoust E., de Vaucouleurs A., de Vaucouleurs G., Fouqué P., Garcia A.M., Kogoshvili N., Hallet N., Mamon G., Miyauchi-Isobe N., Odewahn S., Prugniel Ph., Simien F., Takase B., Turatto M. and many other people who send some useful comments.
We want also to express our gratitude to some Institutions for their financial support: The "Ministère de l'Enseignement Supérieur et de la Recherche", The "Conseil Régional Rhone-Alpes" and the "Centre National de la Recherche Scientifique".
We would like to emphasize an important decision for the future: we will maintain the same reduction procedures for a full year (unless errors are found) in such a way users can clearly reference the data, for instance as LEDA1996. Any changes will be announced in the LEDA news. The data of previous years will be accessible on request.