Here, we investigate CAT02 and HPE triangles in both x,y and u',v' spaces. The findings of this study are key for solving the Yellow-Blue and Purple problem simultaneously. At the same time, some inaccurate descriptions concerning the HPE triangle in the literature are discussed.
Changjun Li, M Ronnier Luo, Manuel Melgosa, "CAT02 and HPE Triangles" in Proc. IS&T 20th Color and Imaging Conf., 2012, pp 195 - 199, https://doi.org/10.2352/CIC.2012.20.1.art00034