Allen, R. G., Pereira, L. S., Raes, D. and Smith, M., 2006. Crop Evapotranspiration. Report prepared for FAO. Water Resour. Develop. Manage. Ser. FAO. Rome. Italy.
Alley, W. M. 1984. The palmer drought severity index: Limitation and assumptions. J. Climate Appl. Meteorol. 23, 1100-1109.
Babb, J. C., Khandekar, M. L. and Garnett, E. R. 1997. An analysis of PNA indices for forcasting summer weather over Canadian prairies with implications for wheat yield and protein. In: Proceeding of the Longe-Range Weather and Crop Forcasting Work Group Meeting III. Canadian Meteorological Center. Dorval.
Bhalme, H. N. and Mooley, D. A.1980. Large-scale droughts/floods and monsoon circulation. Mon. Wea. Rev. 108, 1197-1211.
Boken, V. K. 2005. Monitoring and predicting agricultural drought. Oxford University Press.
Byun, H.R. and Wilhite, D.A. 1999. Objective quantification of drought severity and duration. J. Climate. 117(6): 935-943.
Edwards, D. C. and Mckee, T. B. 1997. Characteristics of 20th century drought in the United States at multiple time scales. Climatology Report. No. 97-2. Colorado State University. Fort Collins. Colorado.
Hayes, M. J. 2000. What is drought? National Drought Mitigation Center. URL://www.drought. unl.edu/whatis/indices.htm.
Hayes, M. J., Svoboda, M. D., Wihite, D. A. and Vanyarkho, O. V. 1999. Monitoring the 1996 drought using the standardized precipitation index. Bull. Am. Meteor. Soc. 80, 429-438.
Heim Jr, R. R. 2002. A review of 20th drought indices used in the United States. Bull. Am. Meteor. Soc. 83, 1149-1165.
Janikow, C. Z. 1993. A knowledge-intensive genetic algorithm for supervised learning. Machine Learning. 13, 189-228.
Kendall, M. G. and Stuart, A. 1977. The advanced theory of statistics. Charles Griffin and Company: London, High Wycombe.
Kumar, V. 1998. An early warning system for agricultural drought in an arid region using limited data. J. Arid. Environ. 40, 199-209.
Kumar, V. and Panu, U. 1997. Predictive assessment of severity of agricultural droughts based on agro-climatic factors. J. Am. Water Resour. Association. 33(6): 1255-1264.
Legates, D. R. and McCabe, G. J. 1999. Evaluating the use of "Goodness-of-fit" Measures in hydrologic and hydroclimatic model validation. Water Resour. Res. 35, 233-241.
McKee, T. B., Doesken, N. J. and Kleist J. 1993. The relationship of drought frequency and duration to time scales. Proceedings of the 8th Conference on Applied Climatology Anaheim. CA. Am. Meteorol. Soc. Boston.
Meyer, S. J., Hubbard, K. G. and Wilhite, D. A. 1993. A crop-specific drought index for corn: I. model development and validation. Agron. J. 86, 388-395.
Moghaddasi, M. 2002. Daily drought monitoring and assessment in Tehran province. M. Sc. Thesis. Tarbiat Modares University. Tehran. (in Farsi)
Palmer, W. C. 1965. Meteorological drought. Research paper No. 45. US Weather Bureau. Washington DC.
Palmer, W. C. 1968. Keeping track of crop moisture conditions, Nationwide: the Crop Moisture Index. Weatherwise No. 21.
Pham, D. T. and Karaboga, D. 1998. Intelligent Optimization Techniques. Pub. Springer.
Quiring,S. M. and Papakryiakou, T. N. 2003. An evaluation of agricultural drought indices for the Canadian prairies. Agric. for. Meteorol. 1, 46-62.
Svoboda, M., LeComte, D., Hayes, M., Heim, R., Gleason, K., Angel, J. and Stephens, S. 2002. The drought monitor. Bull. Am. Meteor. Soc. 83, 1181-1190.
Thompson, L. M. 1988. Effects of changes in climate and weather variability on the yields of corn and soybeans. J. Produc. Agric. 1, 20-27.
Thornwaite, C. W. 1948. An approach toward a rational classification of climate. Geogr. Rev. 38.
55-94.
van Rooy, M. P. 1965. A rainfall anomaly index independent of time and space. Notos 14, 43-48.
Walker, G. K. 1989. Model for operational forecasting of western Canada wheat yield. Agric. For. Meteorol. 44, 339-351.
Wells, N. 2003. PDSI Users Manual: Version 2.0. National Agricultural Decision Support System, University of Nebraska-Lincoln.
Wilhite, D. A. and Neild, R. E. 1982. Determining drought frequency and intensity on the basis of plant response: Wild hay in the sand hills of Nebraska. USA. Agric. Meteorol. 25, 257-265.
Wilhite, D. A. and Glantz, M. H. 1985. Understanding the drought phenomenon: the role of definitions. Water International. 10(3): 111-120.
Wu, H. and Wilhite, D. A. 2004. An operational agricultural drought risk assessment model for Nebraska. USA. Natural Hazards. 33, 1-21.
Zhang, J. 2004. Risk assessment of drought disaster in the maize-growing region of Songliao Plain, Chaina. Agric. Ecosyst. Environ. 102, 133-153.