Thermodynamics' 0-th-Law in a nonextensive scenario
  Tsallis' thermostatistics is by now recognized as a new paradigm for statistical mechanical considerations. However, it is still affected by a serious hindrance: the generalization of thermodynamics' zero-th law to a nonextensive scenario is plagued by difficulties. Here we show how to overcome this problem. 
S. Martinez, F. Pennini, and A. Plastino