1. Caroni C, Crowder MJ, Kimber AC (2002a) Discrete frailty models for heterogeneity in lifetime distributions. In: Stasinopoulos M, Touloumi G (eds) Proceedings of the 17th international workshop on statistical modelling, pp 157–162
2. Caroni C, Crowder MJ, Kimber AC (2002b) Discrete frailty. In: Langseth H, Lindqvist B (eds) MMR 2002: 3rd international conference on mathematical methods in reliability. NTNU, Trondheim, pp 135–138
3. Caroni C, Kimber AC (2004) Detection of frailty in Weibull lifetime data using outlier tests. J Stat Comput Simul 74: 15–23
4. Crowder MJ (2001) Classical competing risks. Chapman and Hall/CRC, Boca Raton
5. Duchateau L, Janssen P (2008) The frailty model. Springer, New York