ESR of YBa2Cu3O7 single crystals : on the nature of the magnetic centres A. Deville, B. Gaillard, H. Noël, M. Potel, P. Gougeon et J.C. Levet J. Phys. France, 50 17 (1989) 2357-2374 DOI: 10.1051/jphys:0198900500170235700