References for th GTK project

[HRahman10 aol com]

Hi!, this is just a genral question.  I am writing a review on GTK, and I 
need references for the following: 

       GTK+,
       GLADE, 
       GIMP,
       GNOME

Would the most appropriate references be the releated web sites, or 
particular people, i.e. developers.

Could someone help me with the references.

And also where can I get add-on libraries for GTK, which I've also mentioned 
in my review?

Thank You!