The Oxford Encyclopedia of the Modern Islamic World by 
Saudi Arabia and the Gulf Arab States Today by Why use Encyclopedias?
Encyclopedias provide an overview and introduction to a topic. Encyclopedias are meant to get you started on a topic and can help you become familar with issues and terminology in a subject area. They will provide you with background information and additional references. They are not research documents.
Encyclopedia of the Persian Gulf War by 
Who's who in the Gulf
Who's Who in Qatar