United States. Bureau of Labor Statistics
and Johnson, Richard N.
Railroad Technology and Manpower in the 1970's : Bulletin of the United States Bureau of Labor Statistics, No. 1717 ,
Washington, D.C:
For sale by the Supt. of Docs., U.S. Govt. Print. Off.,
1972, https://fraser.stlouisfed.org/title/4830,
accessed on September 12, 2024.