1. Das AK, Das M, Das A (2020) Fundamental Concepts of Inorganic Chemistry - Vol. 1 (3rd Edn.). CBS Publishers & Distributors, New Delhi, pp. 201–203. ISBN: 978–93–89566–97–3
2. Das AK, Das M (2019) Fundamental Concepts of Inorganic Chemistry – Vol. 7 (1st Edn. 3rd Reprint). CBS Publishers & Distributors, New Delhi, pp. 1992–2002. ISBN: 978–81–239–2354–3.
3. Wald G (1968) The molecular basis of visual excitation. Nature 219:800–807. https://doi.org/10.1038/219800a0
4. Das A, Das U, Das AK (2022) Present state of knowledge of chemistry of our vision: photoreceptor molecules and vision cycle. Asian J Org Med Chem 7:309–320. https://doi.org/10.14233/ajomc.2022.AJOMC-P409
5. Das AK, Das A, Das (2021) Biophysical, Bioorganic & Bioinorganic Chemistry (2nd Edn.). Books & Allied (P) Ltd, Kolkata, pp 194–205. ISBN: 978-81-948455-2-2