United States. Bureau of Labor Statistics. "Tomorrow's Manpower Needs: Volume IV" in Tomorrow's Manpower Needs: National Manpower Projections and a Guide to Their Use as a Tool in Developing State and Area Manpower Projections : Bulletin of the United States Bureau of Labor Statistics, No. 1606 (1969). https://fraser.stlouisfed.org/content/?item_id=498430&filepath=/files/docs/publications/bls/bls_1606_1969_v4.pdf, accessed on May 23, 2018.