||Valko M et al., Redox- and non-redox-metal-induced formation of free radicals and their role in human disease. Arch Toxicol. 2016 Jan90(1):1-37. doi: 10.1007/s00204-015-1579-5 p.4 right column 4th paragraphPubMed ID26343967
||Kakhlon O, Cabantchik ZI (2002) The labile iron pool: characterization, measurement, and participation in cellular processes. Free Radic Biol Med 33 :1037–1046. doi:10.1016/S0891-5849(02)01006-7 AND Wang J, Pantopoulos K (2011) Regulation of cellular iron metabolism. Biochem J 434: 365–381. doi:10.1042/BJ20101825PubMed ID12374615, 21348856
||P.4 right column 4th paragraph: "Only a very small amount of iron is present in the form of a redox-active iron pool, sometimes termed as the labile iron pool (LIP), which represents iron bound to low-affinity intracellular low molecular weight ligands. It has been estimated that less than 5 % of the total cell iron is present in the redox-active form (50–100 μM) (primary sources). The presence of a free redox-active iron pool in a cell may serve as a catalyst for the formation of free radicals via the Fenton reaction (eq.4) which may cause damage to cellular components."