The Swift satellite rapidly and accurately localises roughly 100 gamma-ray bursts (GRBs) per year. An ongoing programme to optimise the legacy value of the Swift mission will be presented: to determine redshifts for as many long bursts as possible. A statistically useful sample of GRBs with measured redshifts, allows a proper investigation of their host galaxies, energetics, luminosity function and their link to the star-formation history of the Universe. I will define the sample and discuss the implications of the true redshift distribution; so far 131 long GRBs have 'observing conditions' favourable for redshift determination with 66 of them with secured redshifts.
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