Takagi, Hiromichi. “Constructing Prime $\mathbb{Q}$-Fano Threefolds of Codimension Four via Key Varieties Related With $\mathbb{P}^2\times \mathbb{P}^2$-Fibrations”. MATHEMATICA SCANDINAVICA, vol. 131, no. 3, Oct. 2025, doi:10.7146/math.scand.a-158550.