In Evaluation of Agricultural Research: Proceedings of a Symposium Sponsored by NC-148 ( Analysis of Returns to Agricultural and Related Research in the North Central Region), Minneapolis, May 12-13, 1980, eds. George W. Norton, Walter L. Fishel, Arnold A. Paulsen and W. Burt Sundquist. (St. Paul, MN: University of Minnesota, Agricultural Experiment Station, Miscellaneous Publication 8-1981, 1981), pp. 76-82