1. S. M. Alcorn, and C. May .1962 .Attrition of a saguaro forest., Plant Disease Reporter,46:156 -158 .
2. Taxonomy and Pathogenicity of Erwinia cacticida sp. nov.
3. The Palmer Drought Severity Index: Limitations and Assumptions
4. J. E. Bowers, 1981 .Catastrophic freezes in the Sonoran Desert., Desert Plants,2:232 -236 .
5. J. E. Bowers, 1994 .Natural conditions for seedling emergence of three woody plants in the northern Sonoran Desert., Madrono,41:73 -84 .