choice. This image is a derivative work of the following images: File:Lens3b.svg licensed with Cc-by-sa-3.0-migrated-with-disclaimers, GFDL-en, GFDL-self-en...
en:User:DrBob/Figures. Converted to SVG by DrBob on 6 March 2006 and uploaded to en:wiki. Derivative works of this file: Lens3b pt.svg македонски I, the copyright...
