Reddy Koduru1, Janardhan, et al. “Enhanced Extraction and Separation of Zr(IV) and Hf(IV) from Acidic Chloride Solutions Using 4-Sebacoylbis(1-Phenyl-3-Methyl-5-Pyrazolone) in Presence of Crown Ethers”. Asian Journal of Chemistry, vol. 26, no. 20, Sept. 2014, pp. 6885-90, doi:10.14233/ajchem.2014.17140.