<a href="http://xxx.lanl.gov/abs/cond-mat/0701763">arXiv
A letter can be found on the
<a href="http://xxx.lanl.gov/abs/cond-mat/0605301"> arXiv </a> or through
<a href="http://www.iop.org/EJ/abstract/0305-4470/39/24/L04/"> JPhysA</a>.
The paper "Probability currents as principal characteristics in the statistical mechanics of
nonequilibrium steady states" can be found either on the
<a href="http://xxx.lanl.gov/abs/cond-mat/0701763">arXiv</a> or via
<a href="http://www.iop.org/EJ/abstract/1742-5468/2007/07/P07012/"> JStatMech</a>.