The CERN Yellow Report series was started in 1955. It provided a medium for communicating the work done at CERN where publication in a journal was not appropriate.
The yellow report series includes the proceedings of schools and of workshops having a large impact on the future of CERN, the series also includes reports on detectors and technical papers from individual CERN divisions, again the criteria being that the audience should be large and the duration of interest long.
The Yellow Reports have to be approved by the CERN Report Editorial Board (CREB), who call for the advice of referees when judged necessary.