Paulino, J. F., et al. “Recovery of Tungsten by Liquid-Liquid Extraction from a Wolframite Concentrate After Fusion With Sodium Hydroxide”. Instituto De Engenharia Nuclear: Progress Report, nº 1, julho de 2015, p. 92, https://revistas.ien.gov.br/index.php/ienprogressreport/article/view/46.