Y. Huang and  Q. J. Tian and  L. T. Du and  J. Liu and  S. S. Li,  Precipitation Change and its Implication in the Change of Winter Wheat drought and Production in North China Region from 2000 to 2010.   journal   = {International Journal of Agricultural and Biosystems Engineering}, [online]. World Academy of Science, Engineering and Technology.
    November 2011, vol. 59(11). 846 - 851
    [viewed 25 May 2020]. Available from: https://publications.waset.org/pdf/10463.