www.strikingimages.com

www.stormguy.com

www.chaseday.com

www.nationalgraphic.com

www.ghcc.msfc.nasa.gov/lisotd_old.html#types

www.ptius.com/pti/consult/dist/gallery/photogallery.htm

Golde, R.H.  Lightning. (London, NY: Academic Press Inc, 1977)