GMRT radio halo survey in galaxy clusters at z = 0.2–0.4 - I. The REFLEX sub-sample T. Venturi, S. Giacintucci, G. Brunetti, R. Cassano, S. Bardelli, D. Dallacasa and G. Setti A&A, 463 3 (2007) 937-947 Published online: 19 December 2006 DOI: 10.1051/0004-6361:20065961