1. Armstrong, J.S.: Long-Range Forecasting: From Crystal Ball to Computer. Wiley, New York (1978)
2. Ascher, W.: Forecasting: An Appraisal for Policy-Makers and Planners. Johns Hopkins University Press, Baltimore (1979)
3. Bee Metro Staff: New K Street Mall Trees Planned along Light Rail Foliage Lost to Trolleys Will Be Replaced. Sacramento Bee, April 5, sec. Metro (1984)
4. Bureau of Labor Statistics: Local area unemployment statistics (2016).
http://www.bls.gov/lau/
5. Button, K.: Transit Forecasting Accuracy: Ridership Forecasts and Capital Cost Estimates. George Mason University, Washington, DC (2009)