The first spectral line surveys searching for signals from the dark agesC. M. Persson, R. Maoli, P. Encrenaz, Å. Hjalmarson, M. Olberg, G. Rydbeck, M. Signore, U. Frisk, Aa. Sandqvist and J. Y. DanielA&A, 515 (2010) A72DOI: https://doi.org/10.1051/0004-6361/200913395
