American Radio Relay League, The A.R.R.L. Antenna Book, Newington Connecticut: American Radio Relay League Inc., 1964
King, Gordon J., The Practical Aerial Handbook, London: Newnes-Butterworths, 1970
Pictures barrowed from the fallowing web sites
http://www.cometantenna.com/
http://www.lbl.gov/MicroWorlds/Contents/Contents.html
http://www.naic.edu/vpublic/vcenter/aovef.htm