Jack E. James, Understanding Caffeine, London, SAGE Publications Ltd., 1997
Jack E. James, Caffeine and Health, London, Academic Press Ltd., 1991
D. M. Forrest, Tea for the British, London, Chatto and Windus Ltd, 1973
P. Griffiths, The history of the Indian Tea Industry, London, Weidenfeld and Nicolson, 1967