Constraining the nature of the most distant gamma-ray burst host galaxies S. Basa, J. G. Cuby, S. Savaglio, S. Boissier, B. Clément, H. Flores, D. Le Borgne and A. Mazure A&A, 542 (2012) A103 Published online: 14 June 2012 DOI: 10.1051/0004-6361/201218882