“…Very often, in growth models, immigration's effects may occur, due to the circumstance that the population is not isolated. In these cases, it is necessary take into account birth-death processes with a reflecting condition in the zero state (see, for instance, Di Crescenzo et al [8], Crawford and Suchard [9], Giorno and Nobile [10], Lenin et al [11] and Tavaré [12]). These processes provide interesting applications in queuing models in which a reflecting boundary must be imposed to describe the number of customers in the system (cf., for instance, Crawford et al [13], Di Crescenzo et al [14] and Giorno et al [15]).…”