EL-Sherbeny, M. Salah, et al. “THE OPTIMAL SYSTEM FOR SERIES SYSTEMS WITH WARM STANDBY COMPONENTS AND A REPAIRABLE SERVICE STATION”. Pakistan Journal of Statistics and Operation Research, vol. 5, no. 1, Jan. 2009, pp. 1-17, https://doi.org/10.18187/pjsor.v5i1.150.