Pottinger, P. “Zur Berechnung Der Absoluten Projektionskonstanten Endlich - Dimensionaler Normierter Vektorräume: On the Calculation of Absolute Projection Constants in Finite-Dimensional Normed Vector Spaces”. Anal. Numér. Théor. Approx., vol. 4, no. 2, Aug. 1975, pp. 161-70, https://ictp.acad.ro/jnaat/journal/article/view/1975-vol4-no2-art7.