1. AGUAYO, V. M., garnier, D. & BAKER, S. K. (2010)Drops of Life: Vitamin A Supplementation for Child Survival, Progress and Lessons Learned in Central Africa, UNICEF, [Online] Available at: http://www.unicef.org/wcaro/english/WCARO_Pub_DropsLifeVitA.pdf (accessed 10 October 2013).
2. ANDERSON, T. (2013)Alfred (Al) Sommer, Science Heroes.com, [Online] Available at: http://www.scienceheroes.com/index.php?option=com_content&view=article&id=74&Itemid=131#Introduction (accessed 10 October 2013).