Abbas, Ismail Ibrahim, Hassan Hasan Hammud, and Hasan Shamsaldeen. 2012. “Calix[4]pyrrole Macrocycle: Extraction of Fluoride Anions from Aqueous Media”. European Journal of Chemistry 3 (2):156-62. https://doi.org/10.5155/eurjchem.3.2.156-162.542.