Usami, Shiro, et al. “Preconcentration of Silver With the Ion-Pair of 1,10-Phenanthroline and Tetraphenylborate on Naphthalene ”. Asian Journal of Chemistry, vol. 1, no. 2, Mar. 2010, pp. 105-11, https://asianpubs.org/index.php/ajchem/article/view/25379.