This article is concerned with the $(r, q)$ inventory model, where demand accumulates continuously, but the demand rate at each instant is determined by an underlying stochastic process. The primary result is the demonstration of a certain insensitivity property, which characterizes the limiting behavior of the model. This property drastically simplifies the computation of performance measures for the system.
"Inventory Models with Continuous, Stochastic Demands." Ann. Appl. Probab. 1 (3) 419 - 435, August, 1991. https://doi.org/10.1214/aoap/1177005875