http://www.ghgcorp.com/cshaw/platform.htm
  http://www.atmpage.com/platform.html
  http://www.rmss.org/gallery/article1.htm
  http://home.HiWAAY.net/~warrenca/Astronomy/Projects/Tracker/Manual.html
  http://members.tripod.com/denverastro/dsdfile/dspfile.htm
  http://www.jlc.net/~force5/Astro/ATM/Poncet/Intro.html
  http://www.johnsonian.com/index.html
  http://www201.pair.com/resource/astro.html/regular/products/eq_platforms/
  http://home.wanadoo.nl/jhm.vangastel/Astronomy/50cmscope/newplatform.htm
  http://home.t-online.de/home/s-haas/Nachfuehrplattform/PlattformBericht.htm        deutsch
  http://www.starhopper.de/astro/plattform/plattform.html           auch deutsch