Swedish postage stamps with Reutersvärd's impossible figures that were printed at 1982. Click on a stamp to see it in better quality.
A first day cover (FDC) with this stamps you can see below. It was found at http://fnys.smult.com/kanda-personer/Breb-kanda-personer-N-O/fnys-O-Reutersv.jpg/view.
Postage stamps that was devoted to mathematical congress in Insbrook in 1981.
This postage stamp is devoted to anniversary of university Technion in Israel. Image of the stamp was found at http://sio.midco.net/danstopicalstamps/impossible.htm
Postage stamps that are ship from shop of the website www.sandlotscience.com.