Can we use Gamma Ray Bursts to probe high redshift star-formation?
  We present a detailed analysis of the selection effects that plague GRB observations. We find that these effects may partially explain the different redshift distributions between BeppoSax/HETE2 and Swift bursts. It is mandatory to consider these effects to determine the redshift evolution of GRBs. 
F. Fiore, D. Guetta, S. Piranomonte, V. D'Elia and L.A. Antonelli