Modeling and simulation of protein elution in linear pH and salt gradients on weak, strong and mixed cation exchange resins applying an extended Donnan ion exchange model Wittkopp, F.; Peeck, L.; Hafner, M.; Frech, C. Journal of Chromatography. a 1545: 32-47 2018 https://eurekamag.com/research/065/324/065324399.php