Quantum topological excitations: from the sawtooth lattice to the Heisenberg chain S. A. Blundell and M. D. Núñez-Regueiro Eur. Phys. J. B, 31 4 (2003) 453-456 Published online: 06 March 2003 DOI: 10.1140/epjb/e2003-00054-2