• A problem in fair division
  How to cut a rectangular pizza with a rectangular hole. Elementary, with pictures. February 2004.
• On a theorem of Krapez
  A nice, not so well-known property of finite groups. October 2002.
• Sum of Cubes
  This illustration demonstrates the fact that the square of the sum of the first n positive integers is equal to the sum of the first n positive cubes. A very similar illustration was first published by Abu Bekr Mohammed ibn Alhusain Alkarchi in about 1010 CE. And it is still true. January 2002.
• Erdoes-Szekeres configuration
  16 points in general position so that no 6 of them form a convex hexagon.
• Projective plane of order 3
  An unusually symmetric picture of the projective plane of order 3. September 1998.