EXPERIMENTAL EVIDENCES FOR AN HALDANE GAP IN QUASI ONE-DIMENSIONAL ANTIFERROMAGNETS J. P. Renard, L. P. Regnault et M. VerdaguerJ. Phys. Colloques, 49 C8 (1988) C8-1425-C8-1429DOI: https://doi.org/10.1051/jphyscol:19888655
