1. Accomplishments and Prospects of Futures Research;Helmer,1973
2. Report on a Long-Range Forecasting Study;Gordon,1964
3. O. Helmer, private correspondence, October 10, 1974.
4. Accomplishments and Prospects of Futures Research;Helmer,1973
5. Comparison of Delphi Forecasting Studies in 1964 and 1969;Ament;Futures,1970