In this paper, we introduce a notion of stationarity for the pair of flows in a metric vector space and characterize it in such a way that there exist two relations, called a dissipation-dissipation theorem and a fluctuation-dissipation theorem, among the -Langevin matrix associated with the pair of flows.
Yasunori OKABE. "On the theory of -Langevin equations for stationary flows (1): characterization theorem." J. Math. Soc. Japan 51 (4) 817 - 841, October, 1999. https://doi.org/10.2969/jmsj/05140817