We consider the symmetry of lattice su(n) spin systems with inverse square exchange; the Haldane-Shastry model and the Polychronakos-Frahm model. It is shown that both systems have yangian symmetry for a finite number of sites. Based on the yangian symmetry the energy spectrum is considered. Furthermore the representation for motifs and the relations with the Virasoro character for su(n) level-1 Wess-Zumino- Witten theory are discussed.
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