- W. C. Fernelius & E. E. Renfrew, Indigo, Journal of Chemical Education, Vol 60 No. 8, August 1983
- C. Ekelem et al, Indigofera tinctoria, Harvard ‘Canvas’ online resource, pdf.
- T. R. Blackburn, A Miscellany of Mutinies and Massacres In India, APH Publishing 2007
- Indigofera tinctoria (true indigo), CABI Invasive Species Compendium (online resource)
- Kumar, P. (2016). Plantation Indigo and Synthetic Indigo: European Planters and the Redefinition of a Colonial Commodity. Comparative Studies in Society and History, 58(2), 407-431.
- N. Wenner, The Production of Indigo Dye from Plants, Fibershed, Dec 2017, online resource
- S. Parvez, Local Indigo Goes Global, The Daily Star (Bangladesh), Oct 30, 2018
See full list of Individual Species References.