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2. Notes on an eruption resembling that of Variola in the skin of a mummy of the 20th Dynasty;Ruffer;J Path Bact,1910
3. Princes and Peasants: Smallpox in History;Hopkins,1983
4. The Greatest Killer: Smallpox in History;Hopkins,2002
5. http://www.who.int/archives/fonds_collections/bytitle/fonds_6/en/.