1. Department of Geosciences; University of Arkansas; Fayetteville Arkansas USA
2. Laboratorio de Dendrocronologia; Instituto Nacional de Investigaciones Forestales, Agricolas, y Pecuarias; Gomez Palacio Mexico
3. Climate Services and Monitoring Division; NOAA National Climatic Data Center; Asheville North Carolina USA
4. Departamento Microbiologia y Parastologia; UNAM Mexico; D.F. Mexico
5. Department of Geography; Southern Illinois University; Carbondale Illinois USA