V. A. Koverga, B. A. Marekha, A. Idrissi, and O. N. Kalugin, “Competition of ion association and solvation in mixtures of BmimPF6 with γ-butyrolactone”, Khark. Univ. Bull. Chem. Ser., no. 24, pp. 40-47, Oct. 2014.