Multiple Timescale Comparison of the Aggregate Drought Index (Adi), the Standardized Precipitation Index (Spi), and Tree Rings in Southern California. AGUFM (2012)
Hydrological and Meteorological Drought Severity in Oregon: Comparisons Between the Surface Water Supply Index (Swsi) and Standardized Precipitation Index (Spi). AGU Fall Meeting Abstracts (2005)
A Comparison of Drought Assessment by the Aggregate Drought Index (Adi) and the Standardized Precipitation Index (Spi). AGU Fall Meeting Abstracts (2004)