Siddiqi, K.S., et al. “Binding Constant: Fluorescence Quenching of Ciprofloxacin With Fe(III) and Zn(II)”. Asian Journal of Chemistry, vol. 22, no. 3, Mar. 2010, pp. 1957-65, https://asianpubs.org/index.php/ajchem/article/view/11361.