Talpur, Mir G. H., and Raja M. Ilyas. “The Marginal Distributions of a Crossing Time and Renewal Numbers Related With Two Poisson Processes Are As Ph-Distributions”. Pakistan Journal of Statistics and Operation Research, vol. 2, no. 1, Jan. 2006, pp. 27-34, https://doi.org/10.18187/pjsor.v2i1.83.