In January 2011, a literature search was performed using the PubMed international databases digital files on the biomedical and health sciences of the "U.S. National Institutes of Health", CINAHL Cumulative Index to Nursing and Allied Health Literature, Cochrane Library, ISI web of Knowledge Science Citation Index and Social Science Citation Index and LILACS Latin American and Caribbean Health Sciences Literature, BVS, limiting the search to between January 2000 and August 2010.
En Enero de 2011 se realizó una búsqueda bibliográfica en las bases de datos internacionales PubMed archivos digitales biomédicos y de ciencias de la salud del "US National Institutes of Health", CINAHL Cumulative Index to Nursing and Allied Health Literature, Biblioteca Cocrhane, ISI Web of Knowledge Social Science Citation Index y Science Citation Index y LILACS BVS, limitando la búsqueda entre enero del 2000 y agosto del 2010.