Integrable quantum spin chains and their classical continuous   counterparts
  We present certain classical continuum long wave-length limits of prototype integrable quantum spin chains, and define the corresponding construction of classical continuum Lax operators. We also provide two specific examples, i.e. the isotropic and anisotropic Heisenberg models. 
Jean Avan, Anastasia Doikou, Konstadinos Sfetsos
hep-th math-ph math.MP nlin.SI