1. Albertus M (2003) Science, optics, and you: pioneers in optics.
http://micro.magnet.fsu.edu/optics/timeline/people/magnus.html
. Accessed 28 May 2013
2. Discovery of Light Sensitive Materials (2013) Photographic chemistry web page.
http://www.bgsu.edu/departments/chem/faculty/endres/projects/photo_history.htm
. Accessed 18 May 2013
3. Leggat R (2002) Schulze, Johann Heinrich, in history of photography.
http://www.mpritchard.com/photohistory/history/schulze.htm
. Accessed 18 May 2013
4. Lundgren A (2013) Carl Wilhelm Scheele. Encycl Britannica.
http://www.britannica.com/EBchecked/topic/527125/Carl-Wilhelm-Scheele
. Accessed 18 May 2013
5. Editors Encycl Britannica (2013) Jean Senebier. Encycl Britannica.
http://www.britannica.com/EBchecked/topic/534381/Jean-Senebier
. Accessed 18 May 2013