This Kohonen Self-Organizing Map is based on a neural network analysis of the keywords associated to the catalogues (see Poincot et al., 1998A&AS..130..183P; and Lesteven et al.,
Each dot marks a map area; colour denotes the density or the
clustering tendency of the documents;
deep blue areas have the lowest density.
Just click any area on the map to get the corresponding list of
catalogues found in that area.