1. WHO Global Health Observatory, http://www.who.int/gho/map_gallery/en/, accessed 28 October 2014
2. City Mayors, http://www.citymayors.com/statistics/largest-cities-population-125.html, accessed 28 October 2014
3. World Cancer Report 2014, IARC, http://apps.who.int/bookorders/anglais/detart1.jsp?codlan=1&codcol=76&codcch=31, accessed 28 October 2014
4. Tumor metastasis: mechanistic insights and clinical challenges
5. Metastasis: a question of life or death