SYMMETRY OF SPIN WAVES AND HALDANE GAP IN CsNiCl3 Z. Tun, W. J. L. Buyers, R. L. Armstrong, E. D. Hallman and D. P. Arovas J. Phys. Colloques, 49 C8 (1988) C8-1431-C8-1432 DOI: 10.1051/jphyscol:19888656