-This draws Escher's ``Impossible Cage,'' a 3d analog of a moebius
-strip, and rotates it in three dimensions. Written by Marcelo
-Vianna.
+This draws Escher's "Impossible Cage", a 3d analog of a moebius
+strip, and rotates it in three dimensions.
+
+http://en.wikipedia.org/wiki/Maurits_Cornelis_Escher
+
+Written by Marcelo Vianna; 1998.