N. Aoyagi, T. Toraishi, S. Nagasaki, and S. Tanaka, “Luminescence and Potentiometric Studies on the Complexation of Europium(III) by Picolinate in an Aqueous Solution”, J. Appl. Sol. Chem. Model., vol. 1, no. 2, pp. 148–155, Dec. 2012.