Correlation structure of the Burrell and Cane mixed Poisson model for library loans with aging is presented and illustrated by data from University of Sussex. The approach is compared and contrasted with that originally formulated by Morse and recently reevaluated by Beheshti and Tague. Directions for future investigations are suggested. (Author)

Utilizing 11 years of University of Saskatchewan circulation transactions, it is shown that P. M. Morse's Markov model of book use fits approximately 99 percent of data for whole collection and for three subject areas; contrary to his assumptions, one of the model's parameters is time dependent. Thirteen references are included. (EJS)