Agnihotri, R., N. Agnihotri, Raj Kamal, and Jaswant R. Mehta. 2010. “3-Hydroxy-2-(3´-Methyl-2&Acute;-Thienyl)-4-Oxo-4H-1-Benzopyran As an Analytical Reagent for the Spectrophotometric Determination of Tungsten(VI)”. Asian Journal of Chemistry 20 (6):4469-76. https://asianpubs.org/index.php/ajchem/article/view/19046.