Zuo, Zhan-fei, and Yi-min Huang. “Absolute Normalized Norms in R^2 and Heinz Means Constant”. Topological Methods in Nonlinear Analysis 60, no. 2 (September 24, 2022): 475–490. Accessed December 16, 2025. https://apcz.umk.pl/TMNA/article/view/40184.