Lee, Hyunjin, Eunmi Pak, and Young Jin Suh. 2015. “Hopf Hypersurfaces in Complex Two-Plane Grassmannians With $\mathfrak{D}$-Parallel Shape Operator”. MATHEMATICA SCANDINAVICA 117 (2):217-30. https://doi.org/10.7146/math.scand.a-22868.