Niemiec, Piotr. “The Electronic Structure of Phosphotungstic (H₃PW₁₂O₄₀) Heteropolyacids Modified by Fe²⁺ Cation”. Science, Technology and Innovation 11, no. 4 (February 2, 2021): 24–32. Accessed May 2, 2024. https://journals.anstar.edu.pl/index.php/sti/article/view/295.