A very narrow gyrosynchrotron spectrum during a solar flare C. G. Giménez de Castro, J. E. R. Costa, A. V. R. Silva, P. J. A. Simões, E. Correia and A. Magun A&A, 457 2 (2006) 693-697 Published online: 12 September 2006 DOI: 10.1051/0004-6361:20054438