"photochromic glass" . "photochromatic glass" . . "photochromic" . "photochromism" . "photochromicity" . . "Photochromism" . "spiropyrans" . "photocromatic" . "photochromism." . . "spiropyran" . . "Photochromic" . . "photochromatic" . "Photochromism" . . "photochroic" . . .