“…Initially, the random mechanism underlying the models was assumed to be independent, but in 1965 Lloyd and Odoom (1965) proposed a model in which a dependent structure was feasible by assuming an underlying Markov chain as part of the random mechanism. The stochastic model was later expanded to having an underlying semi-Markov process, and a specific one-compartment storage model with underlying semi-Markov process was considered by Puri (1978), Puri andSenturia (1972), (1975), Balagopal (1979), Puri and Woolford (1981), and Puri and Tollar (1985), and others.…”