MAGNETISM OF A TWO-DIMENSIONAL XY SYSTEM : NEUTRON STUDIES OF CoCl2 INTERCALATED GRAPHITE J. Rogerie, Ch. Simon, I. Rosenman, J. Schweizer, Ch. Vettier, R. Vangelisti et P. Pernod J. Phys. Colloques, 49 C8 (1988) C8-1437-C8-1438 DOI: 10.1051/jphyscol:19888659