Jumean, F.H. “Thermodynamics of the Second Ionization of Piperazine- N,N&Acute; -Bis(2-Ethanesulfonic Acid) in Water and in Aqueous Methanol”. Asian Journal of Chemistry, vol. 4, no. 3, Mar. 2010, pp. 579-87, https://asianpubs.org/index.php/ajchem/article/view/25099.