When Is a Storage Function a State Function in Discrete Time?

@article{Kaneko2003WhenIA,
  title={When Is a Storage Function a State Function in Discrete Time?},
  author={Osamu Kaneko and Takao Fujii},
  journal={SIAM J. Control and Optimization},
  year={2003},
  volume={42},
  pages={1374-1394}
}