The Deep Web, also known as the Invisible Web, is a portion of the web not reached by standard search engines such as Google and Bing. Less than 10% of the web is indexed by search engines with the remaining 90% of web content called the Deep Web. It is estimated to be 2-500x bigger than the surface web.
Content on the Deep Web is not found by most search engines because it is stored in a database which is not coded in HTML. Google and Bing might lead us to a front door [a search interface], but it generally can't search the content of a databse. It is up to you to search the database where the results of your search are loaded into a dynamically generated HTML page for viewing.
For more info, see What is the Deep Web? story from CNNtech.
Here are a few ways to search for content on the Deep Web:
Make the mental shift from find the content to find a doorway to the content.
In your community:
Consider where experts may be in your community - association, business, government, hospital, organization, university, etc.
Explore their websites for:
When all else fails, call the organization's office and ask if anyone is available to speak to you about _____________.
Through local news:
Search the archives of your local news - newspapers, radio, TV - for stories related to your topic. Which experts were interviewed in those stories? Start by searching the Access World News USA Washington database or go directly to issues of these newspapers:
See the Libraries' News research guide for more databases including Global Newsstream and PressReader.
Through scholarly publications:
If you find a scholarly journal article related to your topic, chances are the author is an expert in that subject. Want to be sure? Check the author's credentials. See how many people have cited the article using Google Scholar or Web of Science. If an article has been cited by many other authors, it'is likely that the original article is significant to the area of research.