I found a description of "Identifying the 17 Plane Symmetry Groups"
 on the web at a site in Italy.
The search engine I was using encouraged me to translate the page.
What follows is the translation the engine provided:

"Situated of the Southern Polytechnic Been University; 
the much clear page on the classification of the 17 groups of the mosaics 
(for everyone comes gives the characters to you distinguished to you of the 
group, beyond to numerous images); cont hyenas deepenings are on the 
mathematical forehead, are on other foreheads (many artistic examples of several ages)."

So watch out for the hyenas deepening your mathematical forehead as you surf here!

Identifying the 17 Plane Symmetry groups