Given these revolutions are all extensively covered in the scholarly and general press, there are far too many specific useful resources to list here. Instead, some general search tips:

• Use Catalyst to find books and articles on the revolution.
• Use the facets on the left to narrow to specific subject areas, just to books or articles, just to reference, or specific publishers like Oxford.
• When you find a book or article that's helpful, use the subject headings to find more like that one. Some sample subject headings (this is just a sampling, usually there are multiple subject headings that apply to any given topic):
  • Soviet Union -- History -- Revolution, 1917-1921 
  • Egypt -- History -- Protests, 2011-
  • Hungary -- History -- Revolution, 1956
  • Iran -- History -- Revolution, 1979