網址: https://www.researchgate.net/profile/Monique-Teillaud/publication/266349529/figure/fig9/AS:667619623436295@1536184330404/The-central-projection-of-u-s-on-p-intersects-the-open-unit-d-ball-B-p-in-p.png
網址2: https://www.researchgate.net/figure/The-central-projection-of-u-s-on-p-intersects-the-open-unit-d-ball-B-p-in-p_fig9_266349529
