1. Stellarium, http://www.stellarium.org/ (Last access June 12, 2013).
2. Cartes du Ciel - SkyChart, http://www.ap-i.net/skychart/start (Last access June 12, 2013).
3. GoogleSky Map, http://www.google.com/mobile/skymap/ (Last access June 12, 2013).
4. Heavens Above;Peat,2013
5. Red is the new black: how the colour of urban skyglow varies with cloud cover