1. Sistema Nacional de Información en Salud. 2005. Disponible en: http://sinais.salud.gob.mx
2. Gastrointestinal cancer in four medical centers in Mexico City. A 25-year study;Villalobos-Perez;Rev Gastroenterol Mex.,2006
3. World Health Organization. World Health Research. 2004. Disponible en: www.who.int/whr
4. AJCC Cancer Staging Manual;Edge,2010
5. WHO classification of tumors of the digestive system;Bosman,2010