1. Fiala, JL (1988) Lilacs, the genus Syringa. Timber Press, Portland, Oregon
2. Goward SN (1989) Satellite bioclimatology. J Climate 2:710?720
3. Hopp RJ (1978) Phenology: an aid to agricultural technology. Vermont Agricultural Experiment Station Bulletin 684, University of Vermont, Burlington
4. Hughes PY, Mason EH, Karl TR, Brower WA (1992) United States historical climatology network of daily temperature and precipitation data. ORNL/CDIAC-50, NDP-042, Carbon dioxide information analysis center, Oak Ridge National Lab, Oak Ridge, Tenn
5. Intergovernmental Panel of Climate Change (1990) Climate change: the IPCC scientific assessment. Cambridge University Press, New York