Occupational Outlook Handbook, 1968-69 Edition : Part 2 : Bulletin of the United States Bureau of Labor Statistics, No. 1550
United States. Bureau of Labor Statistics. "Occupational Outlook Handbook, 1968-69 Edition : Part 2 : Bulletin of the United States Bureau of Labor Statistics, No. 1550," Occupational Outlook Handbook (1968). https://fraser.stlouisfed.org/title/3964/item/498298/content/pdf/bls_1550_1968_2, accessed on April 19, 2024.