Hodnett, BK., & Delmon, B. (1984). Influence of the Phosphorus Vanadium Ratio On the Solid-state Chemistry and Redox Properties of Vanadium Phosphate-based Catalysts. Journal of Catalysis, 88(1), 43-53. https://doi.org/10.1016/0021-9517(84)90048-4 (Original work published 1984)