EYSHI REZAEI, E., A. MOHAMMADIAN, M. KOOHI, and M. BANNAYAN. “Comparative Analysis of Drought Indices for Drought Zone Scheme of Northern Khorasan Province of Iran”. Notulae Scientia Biologicae, vol. 3, no. 3, Aug. 2011, pp. 62-69, doi:10.15835/nsb336170.