Keywords: Bjorn Borg Hollow Face.jpg A mask of Swedish tennis player Björn Borg used in experiments of the en Hollow-Face illusion at Uppsala University Sweden On this picture the mask looks convex but this is an illusion - see Image Bjorn_Borg_Hollow_Face-concave jpg 2004-11-15 own assumed Skagedal de Bild Bjorn Borg Hollow Face jpg Björn Borg Hollow mask illusions |