P. de S. Medeiros Pina Ximenes, A. S. Alves da Silva, T. Stosic, J. F. de Amorim, and R. S. Cezar Menezes, “Analysis of drought severity in Agreste Pernambucano using standardized precipitation index”, Sigmae, vol. 8, no. 2, pp. 331–339, Jul. 2019.