A candidate gravitational lens in the Hubble Deep Field
  The discovery of HDF~J123652+621227, a candidate gravitational lens in the HDF, is reported. This lens may be multiply imaging several optical sources at different redshifts. If follow-up spectroscopy of the lens and the brightest image confirms this hypothesis, observations of this system alone can be used to obtain an estimate of the redshift distribution at extremely faint flux levels. 
David W. Hogg, Roger Blandford, Tomislav Kundi\'c, C. D. Fassnacht   (Caltech) and Sangeeta Malhotra (IPAC,JPL)