When a major U.S. city recognized that over 70% of its IT staff was eligible to retire within a three-year period, they immediately put into place a plan to start bringing in new IT staff and pairing them with the experienced veterans. Because their IT systems were almost exclusively developed in-house over 20 years, organizational IT knowledge was critical, and those required skills could not be obtained on the open market. Does this suggest another area that should be addressed in crisis management and contingency planning? In which plan or document should this issue have been addressed already? (citation is required)