All used textures should be distrubuted under free license
marble.jpg		https://www.rawpixel.com/image/327647/closeup-marble-textured-background	by Teddy Rawpixel
marble-blue.jpg		https://www.pexels.com/photo/gray-and-blue-surface-988871/
timbercut.jpg		https://www.pexels.com/photo/brown-close-up-hd-wallpaper-surface-172289
antique.jpg		https://www.pexels.com/photo/abstract-ancient-antique-art-235985/
pergamena.jpg		https://www.freepik.com/free-photo/old-paper-texture-background_1007802.htm
stone.jpg		https://www.wildtextures.com/free-textures/grungy-yet-elegant-elevation-stone-ii
mars.jpg		https://www.solarsystemscope.com/textures/download/2k_mars.jpg
mercury.jpg		https://www.solarsystemscope.com/textures/download/2k_mercury.jpg
mauritania.jpg		https://go.nasa.gov/2Ugu9M8							NASA Worldview (Jan 24, 2019)
iran.jpg		https://go.nasa.gov/2FNmiT5							NASA Worldview (Jan 24, 2019)
spain.jpg		https://go.nasa.gov/2FMDPuu							NASA Worldview (Jan 24, 2019)