1. The Magnitude of Agricultural Maintenance Research in the USA
2. L. Blakeslee , 1987 . Measuring the requirements and benefits of productivity maintenance research, in evaluating agricultural research and productivity. In: Proceedings of a Symposium, Atlanta, Georgia, 29-30 January, Miscellaneous Publication "52". Minnesota Agricultural Experiment Station, University of Minnesota, Saint Paul, MN.
3. L. Carrol , 1994 . Through the Looking Glass, Penguin Popular Classics. Penguin, London (first published in 1872).
4. Likelihood Ratio Statistics for Autoregressive Time Series with a Unit Root