Unveiling multiple AGN activity in galaxy mergers
  In this paper we present an overview of the MAGNA (Multiple AGN Activity)
project aiming at a comprehensive study of multiple supemassive black hole
systems. With the main goal to characterize the sources in merging systems at
different stages of evolution, we selected a sample of objects optically
classified as multiple systems on the basis of emission line diagnostics and
started a massive multiband observational campaign. Here we report on the
discovery of the exceptionally high AGN density compact group SDSS~J0959+1259.
A multiband study suggests that strong interactions are taking place among its
galaxies through tidal forces, therefore this system represents a case study
for physical mechanisms that trigger nuclear activity and star formation. We
also present a preliminary analysis of the multiple AGN system
SDSS~J1038+3921.}
