OLASORE, A. J., A. E. OLAGBAIYE, T. A. AJAYI, and P. O. ALABI. “Drought Monitoring in Northern Nigeria Using Four (4) Indices.”. International Journal for Research in Applied Sciences and Biotechnology, Vol. 8, no. 1, Jan. 2021, pp. 13-31, doi:10.31033/ijrasb.8.1.3.