1. National Farm Medicine Center, Marshfield Clinic Research Institute, Marshfield, Wisconsin, USA
2. Central States Agricultural Safety and Health Center, University of Nebraska Medical Center, Omaha, Nebraska, USA
3. Division of Society and Environment, University of California Berkeley, Berkeley, California, USA
4. Deprtment of Anthropology, University of Barcelona, Barcelona, Spain
5. Catalan Institute for Research and Advanced Study, Barcelona, Spain