1. American Wind Energy Association, 2013. 2012 U.S. Wind Industry Annual Market Report. 〈http://www.awea.org/annualmarketreport2012〉.
2. American Association of Railroads, 2014. Railroad Statistics. 〈https://www.aar.org/StatisticsAndPublications/Documents/AAR-Stats.pdf〉.
3. Issues in Estimating the Employment Generated by Energy Sector Activities;Bacon,2011
4. Bureau of Economic Analysis, 2014. Benchmark Input–Output Data. 〈http://www.bea.gov/industry/io_benchmark.htm〉.
5. Bureau of Labor and Statistics, 2014. National Industry-Specific Occupational Employment and Wage Estimates. 〈http://www.bls.gov/oes/tables.htm〉.