1. German Industry and Global Enterprise BASF: The History of a Company;Abelshauser,2004
2. Eco-friendly dyes of India;Balaram,2011
3. Indigo;Balfour-Paul,1998
4. Chapter 1 – Indigo – A unique dye with a colourful story;Balfour-Paul,2006
5. Dye plants in Europe;Biertmpfel,2009