Centro Vasco de Arquitectura
Euskal Herriko Arkitektura Ikerkundea
http://www.wikiart.org/en/caspar-david-friedrich/cross-in-the-mountains-1806
http://www.wikiart.org/en/caspar-david-friedrich/wc-cross-in-the-mountains-tetschen-altar-1808-1808-new-masters-gallery-dresden-height0-115-cm
http://www.wikiart.org/en/caspar-david-friedrich/wc-croix-et-cath-drale-dans-la-montagne-1812-1812-museum-kunstpalast-height0-45-cm-17-7-in