The Knob_*.png figures are taken from

  http://itweek.deviantart.com/art/Knob-Buttons-Toolbar-icons-73463960

"This pack includes thirty-nine icons in PNG, ICNS, TIFF and ICO
formats, Mac and Windows compatible, 32x32 pixels dimensions only. You
are free to use these icons on your software application, website,
etc. You're welcome to give credits for the graphics, when used."
Posted by iTweek: http://itweek.deviantart.com/


The lyx_*.png figures are taken from
http://www.karakas-online.de/mySGML/lyx-admonitions.html

The small_*, yellow_pen_*, handwritten_*, question_*,
prev4.png, next4.png, lab1.png, discussion1.png, exercise1.png,
icons are taken from
http://www.iconfinder.com (licence free images).

