I have been in the work force for ca. 15 years. Some of my professional references and former supervisors have retired, died, moved to other companies and/or withdrew from the labor force due to motherhood etc. I am a good worker so my references are usually "stellar." What is the best way to keep these references for career and proof of experience purposes,: although many of them have moved on to other companies or stations in life? What if a potential employer were to call the company and nobody there remembers me or my work becuase there has been so much turnover and none of my listed supervisors work there anymore?