1. American Business and Older Employees: A Summary of Findings,2000
2. Air Traffic Controller Career Programs. Public Law 92–297, May 17, 1972, 86 Stat., pp. 141–145.
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4. Training older workers: implications for HRD/HPT professionals;Allen;Perform. Improve. Quart.,1998
5. American Association of Railroads, April 28, 2004. Washington Press Release: Railroads Expect to Hire More than 80,000 New Workers Over the Next Six Years.