Covariant Thermodynamics of an Object with Finite Volume
  A covariant way to define the relativistic entropy of a finite object has been proposed. The energy-momentum of an object with finite volume is not a covariant physical entity because of the relativity of simultaneity. A way to correctly handle this situation is introduced and applied to the calculation of entropy. The result together with van Kampen-Israel theory gives simple and self-consistent relativistic thermodynamics. 
Tadas K. Nakamura