raie à 21 cm
1994 / 21 cm line of atomic hydrogen / J. W. V. Storey ; M. C. B. Ashley ; M. Naray ; J. P. Lloyd / American Journal of Physics 62 (1994) p. 1077 [doi]
2006 / Cosmology at low frequencies: The 21 cm transition and the high-redshift Universe / Steven R. Furlanetto ; S. Peng Oh ; Frank H. Briggs / Physics Reports 433 (2006) p. 161 [doi]