Bond Algebras and Exact Solvability of Hamiltonians: Spin S=1/2   Multilayer Systems and Other Curiosities
  We introduce an algebraic methodology for designing exactly-solvable Lie model Hamiltonians. The idea consists in looking at the algebra generated by bond operators. We illustrate how this method can be applied to solve numerous problems of current interest in the context of topological quantum order. These include Kitaev's toric code and honeycomb models, a vector exchange model, and a Clifford gamma model on a triangular lattice. 
Zohar Nussinov, Gerardo Ortiz