Answer:
Search the World Wide Web for pages or sites containing key words related to your subject.
Explanation:
This is one of the ways in which you can narrow your subject of research. If you look online for pages or sites that contain key words related to your subject, these key words will most likely give you an indication of the kind of topics that exist in this subject. By gathering this information, you can chose to focus on a particular concept, time period or any other small category that will narrow your focus.