Chapter 1. Introduction -- Chapter 2. Random Age Replacement Model -- Chapter 3. Replacement Model with Minimal Repair -- Chapter 4. Periodic Replacement Models -- Chapter 5. Extended Replacement Models -- Chapter 6. Which is Better for Standby or Parallel Systems -- Chapter 7. Which is Better Problems in Shock and Damage Models -- Chapter 8. Which is Better Problems in Backup Models -- Chapter 9. Which is Better Problems in Checkpoint Models -- Appendix A: Extended Failure Rates References -- Appendix B: Answer to Selected Problems -- Index.