Finding information about the basics of an advanced math topic Yesterday I attended a seminar talk titled "Cluster presentation of reflection groups", and before it I tried to ask Google what is a "cluster presentation" --- but all one can find on this request is about databases or social studies.
Another example: try to find something on "geometrical groups" and not "geometric group theory".
I think this is a very common problem, when you are interested in some area you don't know anything about and trying to find some texts on it --- but it's very hard if you don't know what exactly to look for. Of course if you have someone to ask, it's not a problem anymore, but usually you don't.
So the question is: how to start learning an advanced topic if you don't have any texts or guidelines about it (and have nobody to ask except for MO community)?
 A: This is just about your first frustrating seminar talk. You might borrow a book by James Humphreys, Reflection Groups and Coxeter Groups. I borrowed this because of this course announcement: http://www.ma.utexas.edu/users/allcock/teaching/Coxeter_groups/Coxeter.html and first homework http://www.ma.utexas.edu/users/allcock/teaching/Coxeter_groups/index.html by Daniel Allcock of U. T. Austin. 
I got plenty of stuff on Google with:  presentation "reflection groups"  so it is the word "cluster" that is a bit too specific.
A: How basic is basic?  An ideal presentation announcement will mention the intended audience, as well as what prerequisites will be assumed and not covered.  A bibliography also will give a few clues.
If the subject has old enough roots or foundations, one can turn to certain compilations for motivation and partial explanations that are pitched to a more general audience which possesses graduate level experience.  I personally like Encylopedic Dictionary of Mathematics from MIT press; others like A Princeton Companion To Mathematics; hopefully this thread will produce a few more titles.
Gerhard "Ask Me About System Design" Paseman, 2011.10.22
