Readers of this list may be interested in my post on "special cases" (e.g. squares and rectangles) that I posted today on my blog .
 

Charles Wells
blog: http://www.gyregimble.blogspot.com/
abstract math website: http://www.abstractmath.org/MM//MMIntro.htm
professional website: http://www.cwru.edu/artsci/math/wells/home.html