FIRST-radio sources in clusters of galaxies
  The detailed identifications of the FIRST and NVSS radio sources with optical objects in APM and in DSS surveys are carried out for 26 rich Abell clusters of galaxies. 99 radio sources are identified with optical objects, 40 have probable identifications, and 187 are not identified from 326 radio sources in the considered fields (within Abell radius of each cluster of galaxies). 20 radio sources are definitely in clusters and 34 can be clusters members with high confidence. Therefore, ~30-40% of the FIRST radio sources can be identified with optical objects on the base of APM and of DSS data. On average, one can find 2 identified sources per cluster. 
A.G.Gubanov, V.P.Reshetnikov (Astronomical Institute of St.Petersburg   State University, Russia)