Dendrogram obtained by applying the Serna & Gerbal (1996) technique for 148 galaxies in the interval 0.015 <  z <  0.040 in a 16 deg² square centred on NGC 4104 (object number 83 in this figure). The main structure is represented by the black labels (numbers). Two small substructures are shown in red and blue, and a few “isolated” galaxies (not strongly bound to any of the three structures) are in grey, on the right side of the horizontal axis. The horizontal dashed line represents our cut to define the substructures (see text).