EVIDENCE FOR THREE DIMENSIONAL MAGNETIC ORDERING IN ErBa2Cu3O7 T. Chattopadhyay, P. J. Brown, D. Bonnenberg, S. Ewert et H. Malletta J. Phys. Colloques, 49 C8 (1988) C8-2169-C8-2170 DOI: 10.1051/jphyscol:19888972