Altun, Ozlen, and Selin Bilcen. “Spectrophotometric Investigation of DL-Tryptophan in the Presence of Ni(II) or Co(II) Ions”. European Journal of Chemistry 3, no. 4 (December 31, 2012): 411–415. Accessed May 9, 2025. https://www.eurjchem.com/index.php/eurjchem/article/view/482.