Streck, Nereu Augusto, et al. “Linking Rainfall Variability in Santa Maria With the Pacific Decadal Oscillation”. Pesquisa Agropecuaria Brasileira, vol. 44, no. 12, Dec. 2010, pp. 1553-61, doi:10.1590/S1678-3921.pab2009.v44.2905.