1. United Network for Organ Sharing Web site. http://www.unos.org. Accessed July 3, 2000.
2. Canadian Institute for Health Information Web site. http://www.cihi.ca. Accessed July 3, 2000.
3. No evidence of pig DNA or retroviral infection in patients with short-term extracorporeal connection to pig kidneys
4. Organizacion Nacional de Transplantes Web site. http://www.msc.es. Accessed July 3, 2000.