Strict Detailed Balance is Unnecessary in Monte Carlo Simulation
  Detailed balance is an overly strict condition to ensure a valid Monte Carlo simulation. We show that, under fairly general assumptions, a Monte Carlo simulation need satisfy only the weaker balance condition. Not only does our proof show that sequential updating schemes are correct, but also it establishes the correctness of a whole class of new methods that simply leave the Boltzmann distribution invariant. 
Vasilios I. Manousiouthakis and Michael W. Deem (UCLA)